I’m extremely insecure after being cheated on.

I don’t know if you would call it cheating but a year ago I caught my partner texting another women asking for nudes and saying he would love to see her naked. It completely broke me because I’m a SAHM and devoted my whole life to him and our kids. I chose to forgive him but it’s been so hard. I can’t trust him with anything. He takes a long poop? My brain is telling me he’s texting another woman. A sex scene comes on? My brain is telling me he’s lusting after the woman. He goes to the store? My brain is telling me he’s flirting with the cashier. How do I make this better? I’m trying to make our relationship work because we have 3 children. It’s hard but i feel like im failing. It’s hard being so insecure. I hate myself and I even dream bad things.