First, it might be worth examining if there's anything you do (or don't do) that impacts his enjoyment of giving head. Are you squeaky clean? Is your general area down there neat and well-kempt? Not everybody likes picnicking in a swamp, cheese factory, or overgrown meadow. Make sure you've made the area inviting.
If you've addressed that, or made sure it's not an issue, then it might be worth chatting with him about it, seeing if there's a reason. Maybe he had a traumatic experience that makes him not like it... (e.g., a priest raped him as a child and blowjobs remind him of that trauma) Maybe he didn't want to hurt your feelings and tell you that you stank down there? Maybe he is fine with a bj, but do you grab his ears and fuck his face like a Fleshlight and he doesn't appreciate that? Maybe you don't warn him that you're about to cum, and your cum tastes terrible because you smoke, drink whisky and eat asparagus?
If all is well in all of those regards and he's just decided he's not into it, then you have to make a calculus as to whether that's a price you're willing to pay? As Dan Savage likes to say, a partner should be "good, giving and game" or "GGG": good in bed, or at least willing to learn and improve; giving of the type of pleasure that their partner needs, within reason; and, game for a bit of adventure, again within reason. If your bf is just being lazy or a dick, you may need to determine if you can live without blowjobs, or live without him. (Dan Savage also likes to say that any model that doesn't come with oral as a standard feature should be returned to the dealership.)
But work the problem first, you might find there's something else going on.
