Baby Mama Drama

So me and my fiancé have a daughter together and he has a son from a previous and I have a son from a previous..

we’ve broken up a few times and when we break up he becomes “good friends” with his ex. This last time he was texting her a lot and making plans to hangout and inviting her over for holidays they normally don’t spend together.

This last time it seemed as if he was trying to see if something was there ?

He claims he never wanted anything and they have been broken up for 3 1/2 years. She’s had numerous boyfriends since him. But I am the only one after her.

I sometimes watch there pic up and drop offs.. well he caught me and got mad..

I know I should trust him but i just don’t... she dresses very provocative and when they went to the water park she wore a one piece letting the girls and ass hang out....

Am I trippin?