Ex Coming Back Into My Life

soooo the last couple days my ex has been on my mind and today he actually asked how I’ve been. then he started to text me. he has a girlfriend and they seem happy and im not trying to be a home wrecker. But I’m not gonna lie since him I’ve only been with one other guy and well the sex was okay. but I’ve been craving that deep good sex. he’s been all up on me today and he keeps looking at me the way he used to look at me (y’all know that look) and I told him to stop but I don’t want him to. If sex comes up in your conversation should I say no or do it anyway. I know it’s mean af to do that to someone because I wouldn’t want it done to me. But if you guys know our relationship then you’d understand. Help what should I do.