What's going on anymore?

My boyfriend has been going through some really tough shit for awhile now but in this last week he's completely loosing himself. I've been here for him, encouraged him, put him first when I was hurting because thats love and because I know he needed me to be that person he could fall apart on. Tuesday he told me that he might have feelings for someone else. We've been dating a good time now and it just broke me. He said "I know I love you but I might have feelings for someone else". We've been through everything you could possibly imagine from his mother tournmneting me and putting me down, tearing him down and trying to control him and our relationship, to not being able to hardly see or talk to each other, several times of thinking we were pregnant, and just so much more. I'm honestly heart broken. Yesterday and today's he's been telling me that's not the case, that he wants me and only loves me that he only wants us and our future and our lives, etc. But when he says that I just think does he mean it? I don't know if he said that he might have feeling for someone else because of him overthinking and not being himself or if he actaully ment it. I've asked him several times, I asked if he wanted to be with me and he said yes that I was the only one.. but I still have what he said in the back of my head. Today he randomly texted me talking about the girl he use to like before me and him were even a thing. He said if she asks you this question just tell her yes. Well I of course started overthinking and was getting upset. I asked him if they were talking now and how many other girls he's talked to because in the last month I've learned he hangs around and talks to this one girl all the time and in total I know of 3 girls he has talked to and never mentioned it to me. (The only reason I say this is because a long time ago he started talking to a girl when we first got together and never told me and I had to find out. He would snap her in the shower, when he was naked, etc. So ever since then I asked him just if he was going to talk to a girl please just let me know). I've been trying so hard to move on and trust him again and now all of that is gone because he said he might have feelings for someone else. He wouldn't respond back and my anxiety grew more. I had his sweatshirt so once we got out I just laid his sweatshirt on his car and left. I usually meet with him and walk with him to his car but I just couldn't do it because I knew I'd just break down. I don't know if I made a mistake by doing that. I saw after the whole thing that he called me and texted me asking where I was. He told me that he wasn't talking to anyone else and that he couldn't do this right now and said I love you. I haven't responded because I don't know if I should. Did I mess up by not walking with him? Have I ruined things for good? Should I text him back? What should I do?