Boyfriend help please :(?

okk... so we've been together for a year and a half. we love each other. but i have some trust issues, and im a pretty jealous person. i just found out that my boyfriend messaged the last girl he was with before me on facebook to apologize for how he lead her on and that he was a jerk. i dont mind him apologizing but some of the things he said make me worried. she asked how we were and he said "good she likes to complain a lot though lol" that upsets me a lot because i would want him to have good things to say. and then she said she is glad he found a good girl and he said "thanks but you were a good girl too i was just stupid." we talked about how upset i was and i was crying and he ured me over and over that he never had feelings for her and if he wanted to be with her he would be and that hes sorry he kept it from me and loves me. i dont think he would ever cheat on me i just cant stop thinking about this... does he miss her? am i overreacting? what should i do?