Girls I need help!!!

Me and my boyfriend have been dating for a year and nearly 2 months. We are still in high school but I think he is my one. I have put up with his dumb self and his stupid decisions he even cheated on me three times(2 if the times was with my close friend) and I am still with him. So today I had one of the only girls I have gotten close to since he last cheated on me tell me that he was texting her and I got hella mad. I have asked him not to have any girls numbers that aren't family on his phone or even text girls that aren't family on his phone and out of respect I don't have any guys numbers or text any guys that aren't family on my phone. When I talked to him about it he said that he was just testing me but he has been acting like he did when he cheated on me before ever since last night. I honestly don't know what to do because I am trying so hard to stay with him but I can't do this with the girls anymore. What would y'all do if y'all were in this situation?