I can't say with certainty what's going on with your friends, but it sounds like they are understanding. It's just difficult for people to adjust. I have friends that are very understanding that slip from time to time. They don't do it maliciously at all. It's just not easy to adjust quickly and things can slip. However, do say something to your friends and let them know how you feel. Just don't confront them in an accusing way. Try to be understanding because it is a learning phase for them as they were used to seeing you differently before your transition. If they are nice and accepting, they will get used to it and things will come around.