My mom's changing us because of her boyfriend?!?

I'm Nicole I'm 15 and my mom has had a lot of boyfriends but this last one Mike is an old friend of hers and she really likes him and I told her I just want her to be happy and he makes her happy. Anyway I've only met him twice and right now is the second time we live in Memphis and are visiting him in Nashville where she wants us to move at the end of the end of the year. It's just everytime we're around him she makes us act like completely different people. I don't get it if we have to live with him why are we all not being ourselves including her.