What do I do?

So I have extreme anxiety and I have it bad in a relationship due to being cheated on and stuff by my ex. my SO works in basically an all male job but this girl started working there, and she is attractive, she knows it and wears booty shorts to work ( her job requires her to bend over a lot), and gives my boyfriend more attention than others. I know I shouldn't worry about it or that anything is going to happen, he's never given me a reason to worry about that kind of thing but that worry of being cheated on again comes in my mind with her and when my brain thinks about it I start freaking out and have really bad anxiety attacks. I just want to know if there is anything I can do to stop overthinking it or get it out of my brain!