He has sex with other women

There's a guy I really like and been talking to for 5 months. Everyone know we're kinda together even though we still don't have title. A month ago I found out he had sex with his girl best friend all the time. He told me it's just for fun and we're not in relationship yet so it's not like he's cheating on me and he really like me so I shouldn't be worry. Yesterday I found out he had sex with his ex. I really don't know what to do. He usually just apologizes and make it up to me by all this sweet things and I just can't help to forgive him but it's getting too much cuz I'm sure there are more girls that he's sleeping with. And I had sex with him one time and I'm very upsetting after found all this stuff out.