I could write an essay on this. In fact, I have written a lot on this:
Forgiveness and
Body Acceptance.
This isn't an easy thing to overcome. You are changing, there is no doubt about that. It's often hard for friends/family to accept when you get healthy. They are used to a different version of you and people don't like change. We naturally prefer routines and habits, so if your friends are used to you drinking and eating crap with them, when you change that routine and stop/slow down drinking and pass on the app, it's a hard for them to wrap their heads around.
A lot of marriages/relationships struggle when one partner changes their lifestyle and the other doesn't. I know my marriage has had rocky patches because of it.
The gym takes time. The longer you go and more confidence you build in yourself the less other people will phase you.
Hang in there, you're worth it.