The worry about proving your love is a very feminine trait. Most men prefer the predictable means of proving your love versus more creative ideas. So proving your love should be about communicating your affections on a wavelength he can appreciate without all the frills and whistles you might associate with a grand gesture.
Show Him How He Shows You
Everyone has a unique way of expressing love. Likewise, everyone has a different way of feeling it. Try a few different methods and see which ones he responds to the most. Once you've got him figured out, do more of those kinds of things.
That said, does he tell you, flat out, he loves you? Does he compliment you on your abilities or other attributes? Does he listen as you spill out all the details of your day? Does he do random little acts of kindness for you and anticipate what you need before you even know you need it? How many times in a month does he bring you a little gift (handmade, a wildflower he picked during a walk, or something he bought) and tell you it reminded him of you, so he had to give it to you?
Sit back and think about the nice things he does for you. This may give you a clue to how to make him feel loved in return.
Write It Out
This could be a written letter he can save, an email, a heart-to-heart where you tell him how much you love him and all the things you appreciate about him, or just a quick, "I love you!" a few times per day. You could even send him a text now and then. Just be careful not to bombard him with them several times per day, or you might come across as creepy rather than lovey-dovey.
Give a Sincere Compliment
Somewhere between the heartfelt conversation that lays it all out for him and the "I love you" in passing, there's the sincere compliment. Do you love the way he smiles? Appreciate the way he helps you carry your bags when you're together, adore the way he treats everyone as if they're the only person in the room and incredibly important? Let him know! This doesn't have to be a long conversation. Just speak up when you notice something. Does the moment always pass before you've processed it enough to comment on it? Brainstorm ahead of time and then when you see him doing something you love, say something.
Random Acts of Kindness
For some people, words are nice, but they go in one ear and out the other. While some people love hearing how much you love them, others don't "get" it until you put those words into actions. Sure, you probably do all sorts of things already, but if you've been together for a long time or you're new at relationships and don't know what to do yet, little actions can go a long way. Do random little things for him that you might apply to a stranger. Do specific little things for him you know he'd appreciate that you wouldn't do for a stranger (like folding his laundry because he hates doing it).
Cook for Him
Have you ever heard the adage, 'The fastest way to a man's heart is his stomach?' There is a certain amount of truth in that statement. If you want a simple, yet direct demonstration of the love you feel for your boyfriend, learn to cook his favorite meal. Preparing the meal is a labor of love, particularly if you are preparing a meal you've never prepared before.
If he is going on a trip, consider packing a lunch. He'll appreciate the gesture and the food. It's also a surefire way to remind him about you when you're not there. Remember, don't go overboard with the lunch or the meal, it doesn't need to be a candlelit dinner or a message on every food item - the actual food will do the talking for you.
Support His Friendships
When a woman is insecure in a relationship, she often becomes clingy. She wants to make every moment about her or believe her boyfriend is focused on her. When he isn't focused on her, it can lead to hard feelings. But it's important, for you as a good girlfriend, to support your boyfriend's friendships and make sure he has the guy time if he wants it. If he and his buddies head out every Friday to play sports or just hang out, let him go. Don't invite yourself along. If he wants to invite you, he will. There's nothing wrong with him having quality time with the guys. If he does invite you, be wary of trying to make yourself the main focus. Enjoy the time with him, observing him with his friends and getting to know them. Sometimes you can learn a lot about your boyfriend through his friends.
Do Something He Loves
Take it a step further and arrange for you to do something you know he would love. That could be a trip to a nearby trail to hike, a visit to a local café he's wanted to try out, a sporting event, a festival, or a movie (or anything else he loves!). Ideally, it'll be for the two of you so you can show you're interested in learning more about his interests. Though you should never pretend to be into something you're not to gain a guy's attention or affection, you can always be curious and supportive. You may even come to love it! If you're not into whatever it is and know he needs to have people with him who share the same interest, suggest an outing for him and his friends, or arrange one with his friends as a surprise (check his schedule first!)
Hugs and Kisses
Sometimes, all it takes to show your love is a whole lot of hugs and kisses. Throw in a massage (from you, not a spa!), and your boyfriend might feel like the luckiest, most-loved guy alive. You can go all out and light candles and find a massage oil with a scent you think he'll enjoy, but use your judgment on whether he's the type of guy who would appreciate those extras or would prefer to keep things simple.
Treat every date with him as a first date. In other words, when you go out together, he gets all your attention. Make every time meaningful, and he will appreciate it more. If you've been together for a long time, you may not feel as playful as you used to. Remember the things you loved most about him and how you used to interact. Don't always let the goofy side hide behind the serious one as time goes on. Let your silly side out, too. Think back to how you spent your early days together and try to replicate those sometimes by going on fun dates.
Be His BFF
What do you love in a best friend? The ability to confide in them and know what you've said will go no further ranks high on the list. Also, they will listen to you. Do these things for your boyfriend. Listen, let him know what he says won't be repeated, and try to give unsolicited advice to a minimum. Use eye contact. Keep your phone face down or in your purse while you're together. Don't just nod and say "mm-hmm" when he's talking about something you don't care about. We all want to feel heard and understood, especially by a significant other, so this one should be a no-brainer in every serious relationship (it isn't, though, so step back and take a look at how good of a job you're doing at acting like a best friend to your guy).
Give Him Gifts
Don't go out of your way to spend money you don't have, but if you see something you can afford and think he'd love it, pick it up for him. Let him know it reminded you of him (in other words, you're saying "I think of you when we're not together"). This could be a silly little toy that takes you back to a funny or sentimental moment on a previous date, something he needs or wants but won't get for himself, or something that represents him or a part of his personality. Make gifts for your anniversaries sentimental or something practical (if he's not into sentimental) that will still mean a lot to him, like tickets to a sporting event he's always wanted to attend.
What Not to Do
You can prove your love in many ways, but if your boyfriend wants intimacy or sex and you are not ready for it, don't do it just to prove a point. Sexual intercourse and intimacy are a mutual expression of shared affection and deeper love; it's not a way to prove anything. If your boyfriend is pressuring you to prove yourself by having sex, it may be time to re-evaluate the relationship.