What do I do?

My boyfriend has been acting off since he got back I realized that he was messaging tons of girls even ones that are my friends or people that I know, like 2 months ago he told me that he was going to get girls to go on the sugar daddy website so they could make money and stuff and now he’s actually doing it he’s spending all of his time making the girls profiles and they are sending him pictures like it’s annoying and he’s using my phone too I just got a new one so he’s using my old I phone 6 like omg idk what to do it makes me so mad he turns away when texting and everything he avoids me (we live together I’m 18 he’s 17)