Honestly, lads... total nuisance!
Do you think that perhaps B wasnt sure how he felt about you when you told him you liked him, and now he knows that you are seeing someone else and he has got a bit jealous and decided that now he knows what he wants?
It seems to me that the guy your seeing now sounds great, you both like each other, and there are no probs there.
Ignore B's friend, if B has something to say he should be saying it himself, not get his mate to do it, and B, for whatever reason, didnt do anything when you told him you liked him, so he cant complain that you are now seeing someone else. B missed his chance, simple as! Dont let anyone make you feel guilty for moving on!
The way I see it, you have been completely honest, you havent messed anyone about, and your happy with your boyf. If B is sulking, tough! All you can do is be honest and tell him that you moved on because he didnt get his act together when you told him you liked him.
It doesnt sound stupid, dont apologise for yourself! Its not your problem that B is sulking and cant even talk to you about it himself and getting his mate to do it!
Cheer up, and enoy being with your boyf! x