I am stuck in the middle between my boyfriend and best friend...my boyfriends a jerk..or was? UGH help?

I'm going through the same thing (Im 15 too). In my opinion you should give your EX another chance because he seems like he truly has changed. Me and my current boyfriend were going through the exact same situation, i gave him 3 chances, the first 2 chances i gave him were horrible he flirted with other girls and even tried to have with one. We are on our 3rd try. So far its going Perfect we've lasted 2 months. So My answer is Yes, Your boyfriend just realized how much he wanted you and yes he has changed he doesn't want to lose you a 3rd time. So Just trust him with your heart ((=