i wish i knew how it felt to be free

my exboyfriend cheated on me. I was recently in the darkest part of my life. Until I met my recent boyfriend. He is sweet, kind, caring, loyal, loving, and understanding. So why do I feel so scared that he is going to go off and do the same thing that my ex did. My current boyfriend isn't that type of person. I try to remind myself that it's just that my brain is kind of hardwired now to sense cheating. My boyfriend hasn't given me any reason not to trust him. but his exes keep showing up around him in random places and I know it's non intentional however, I sense a certain darkness there and I don't know how to react to this. Please give me some advice or something to say to him to get me to not feel so bad. I need help.