What is wrong with him???? Does he just not care about me?

Was I just completely played? I'm 18 and have been dating a 45 year old man since June. I saw him making kissy faces to a woman on instagram in August, flipped out and dumped him because I didnt buy his explanation. From then on I kept dumping him and told him I couldnt trust him. I love him but said it wouldnt work. He always came back and found a way to weasal his way into my life and be with me again. He claims he has never cheated on me when we are together but that he talks to other girls only when we are broken up. My mom hates him and sent him a bunch of nasty texts yesterday. She basically has exhiled me because of him and doesnt want anything to do with me. This morning he said it was too much for him to take and that he wanted me to make ammends with my mom even if it was at his expense. So he basically broke up with me. What the hell? After everything we have been through and the times I stayed and now hes the one doing the dumping?