Question about my relationship?

ok, soooo my boyfriend was being a huge dick to me and all this was before prom, so i ended up breaking up with him after he had spent all this money on his ticket and tux(he isnt in highschool so he didnt end up going anyways) and gave his ticket to someone else, then i led him on after prom but then ended up going out to a party at the beach. The next weekend i did the same thing, led him on and then went out to make me feel better and get over him. but i wanted to still be with him in the end so we got back together. welll... everything was good until one night when i was staying at his house i woke up early and his facebook was up and just being curious i looked at his messages and there were like two from girls he had messaged the night before from which he had obvisously forgotten to delete. saying "please dont tell my girl we talked" calling the girl "sweetie" and trying to comfort her bc her bf hit her or something? but he didnt even KNOW her. anyways.. he said it was because he was insecure about our relationship because he was so messed up over what i did to him at prom that he thought i was going behind his back and to keep him sane. I know for a fact he was just messaging them, he wasnt trying to hang out with them. I read all of it. but my question is... are we even? like should i really blame him for messaging other girls and should i forgive him and understand his feelings were still hurt about the whole prom thing and forgive him and just call it even? pleasee help.