Opinion on this. Short !!

This guy and I are talking for a while now. He mentions the future and his last name being mine, etc. We had sex, hung out many times, talks about me living with him in the future. Were not dating yet though.

He went to a party and was hooking up with girl, etc.

I know we’re not dating but this doesn’t seem right that he’s doing that stuff to me.

Opinions?