This is an ex fling from around a year ago, he’d always been flirty but I assumed this would stop when he got a girlfriend. But it hasn’t. It started off with just staring at me and social media stalking me (I think his girlfriend made him remove me), I decided to just ignore. Then it escalated to him approaching me, complimenting me, teasing me and eventually physically touching me and talking about having sex with me. I obviously pointed out he has a girlfriend, but this doesn’t stop him. Whenever he’s with his girlfriend he will just completely ignore my existence. I’ve watched other interactions with women he has in social settings I’m in and he does not do any of this to them. It’s like his face literally lights up when he sees me, I feel like he has this intense attraction towards me. My question is, how do I set a clear boundary and if I were to set a boundary would that be me overreacting? To me his behaviour appears to be emotional cheating, and I do not want to be a part of that.