If you love him than you sacrifice (he should do the same for you). Accepting a marriage proposal and then walking down the aisle is a commitment that you'll love him regardless of how much sex you have. However, it's also a promise that sex 20 or 25 times every 2 years is enough for you. Is it? Can you live with having sex 12-15 times a year for the rest of your life?
My husband doesn't want sex as much as I do but he sacrifices for my happiness as well as me sacrificing my contentment for him, I'll squirm for a few more days until he works up the stamina to give me a nice good railing. Has your boyfriend done that for you? Has he pushed aside his little interest in sex in order to fulfill your needs? If your answer is "no", than is this really someone you want to dedicate the rest of your years to?
Unfortunately, when we have sex before we find our "one", it leaves the option of being able to compare our "one" with the others before them. We often size up and say- "well, his dick's a little smaller than so and so" or "I wish he ate my pussy like blah blah", or "he just doesn't have the stamina of bachelor #5". If you're comparing him to other people than chances are he isn't the one. If you're already thinking about what he is and what he isn't than it sounds like there's some doubt within you that the relationship just isn't working.
If you're looking for options because you do want to stay with him, Have you discussed open relationships so that you can feel fulfilled while still in a romantic relationship with him?
Have you bought a few sex toys and proposed the idea of using them to him? Or left them on the bed for him to find?
Have you laid naked in your bed waiting for him to come home? Do you greet him at the door in sexy negligee?
Do you text him dirty messages or even naughty pictures to get the thought in his head that, "hey, maybe today is a good day to have sex!" ?
Have you put a porno on in hopes to pique his interest?
Have you dropped his pants while he was doing dishes, his taxes online, checking sports scores etc. and given him a blow job right then and there?
If you've exhausted all resources and your lack of sexual activities is making you unhappy than re-evulate your relationship. Trust me, it's better to be open and honest now and move out before hearts are broken than to live the remainder of your life in a sexless marriage that has made you absolutely miserable.