How can you learn to trust someone new, after being lied to, manipulated, betrayed by someone in the past? Has anyone ever done it?

I'm trying to let go of what I cant control. I can't control him. As much as I want to. If I do, he will only leave me. What scares me is the unknown. People can physically or emotionally cheat and lie about it. They cover it up because it's the easy cowardly way out.
What if he's emotionally cheating on me now? He's surrounded by young fit women at work. He probably checks them out or imagines them without clothes. Haha. He's a guy. Guys a visual sexual beings. What if a connection goes too far or he gets bored of me. I don't think we spend quality time together anymore. It's like I'm just a housemate. Someone to chill with and watch tv with at the end of the day. I hate my body I hate myself.

Has anyone got any thoughts to help let go of what you can't control?