This might sound pedantic, but define 'big boobs'. Do you mean big boobs for her frame, or do they have to be boobs so big they'd even look big on a big woman? You see, you say you like a D cup and up, but I have tiny boobs, yet because I have a tiny rib cage they are about an F. Most people have a very poor grasp of bra sizing - an E or F cup is actually about average.
Now for some more constructive advice. If this deal-breaker really affects you or you think there is some deep-seated reason for it, by all means go and talk to someone about it. If you don't think it's that serious, then I guess you'll just have to accept it. If you think it's going to make finding a girlfriend difficult, work on being happy as a single man, and I guess that the more women you meet, the more likely it is that you will meet one with breasts to your liking.
I do think that maybe you are being a little harsh on yourself, though. It's great that you are introspective, but remember that a lot of people have a certain thing they are very picky about when it comes to romantic partners. And it's not like you are dismissing smaller-breasted women on every level, as you are still acknowledging their qualities and worth - you are just perhaps silently ruling them out as sexual and romantic partners for yourself. As long as you are not obnoxious about it, you are entitled to not find something attractive. Keep on meeting women with both friendship and romance in mind, and also remember that just because you haven't found a smaller-breasted woman attractive so far, it might not always be that way. You might be surprised.