First, I should congratulate you on your coming out, yours and your girlfriend’s. I don’t know how old you are but it’s always too many years spent in this dark closet. When we finally decide to get out of it, it seems that all our problems are over but that’s not always the case. Too often, we come across people with homophobia, even if it’s in the lighter sense of the word. We can deal with the one from strangers but from people close to us, it always hurts, even if we don’t let it show.
After the moment (days, weeks or months) of shock following the announcement, life goes on for us. But for our entourage, a full realization of the problem is needed: they have to face they’re own prejudice against homosexuality. Sadly, that’s not something that everybody is willing or able to do. In that case, they will start seeing you differently and that’s how they start to tell you that you’ve changed but you didn’t in a way. It’s because they look at you trough another set of lenses so to speak. So they wait for the mannerism, the different voice intonation or posture (that was always there) and now they see it as being caused by your queerness. Of course, we do change in a way since we get more confident in ourselves and start to show that we’re proud of who we are as gay people but should that be held against us: surely not after all w e’ve been through coming out!
I fear there is nothing you can do about this kind of situation but stay who you are. You’d have to be able to change they’re way of thinking and nobody has that power I’m afraid. Your main purpose in life is to please nobody but yourself (surely your girlfriend too but that’s a totally different subject!). You write in your question that you are happier people and having a great relationship, what more do you need? Life goes on for everybody and in they’re own time they’ll get use to see you as you really are and stop bothering you with it, I’m sure.