My boyfriend is so good to me but I always get intrusive thoughts that he’s cheating, how to stop them?

It’s unhealthy.. I've gone on the dating app we met on again just to check and see if he was still on there.. but he isn’t. I don’t think he’d have enough time in the day to cheat though he still talks to his ex of 4 years which concerns me
My boyfriend is so good to me but I always get intrusive thoughts that he’s cheating, how to stop them?
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