Am i stupid?

so I need advice from people who aren’t my family or friends.

I was dating this guy for about two months we hit it off great honestly felt like I’ve known him for years! The relationship was amazing while it lasted but for some reason the my trust for him wasn’t fully there, so my best friend texted him one day acting to be a girl he meet at a club, she asked if he was talking to someone and he simply said no I’m not. But me and him were dating according to him he knew it was me. So we broke up because I was the only one who fucked up. Time went by we started talking again but then I ended up being at the wrong place at the right time that I saw him getting out of a restaurant with another girl when he was saying he was at home not feeling well. I stopped talking to him for about 1 months then we started talking about and last night I seen him with another girl when earlier that day we were talking about meeting up at his house to have sex.. I texted him saying “ I was stupid for believing you” and all he said was “why are you tripping” because for him he wanted to have sex first and see how he felt after If he wanted to be more than friends. I’ve been there for him and helped him and i don’t know why he always does this.