insecure

So I've been having sex with my ex because I feel it's better then being with someone new. But I can't stop feeling insecure during it epically when he's looking at me. I try to get out of my head but I cant especially since we are not together anymore the whole time I'm just think omg what if his parents come home it would be so awkward since we're broken up. Any tips to help get out of my head.