I feel terrible.

My ex (LLM) and I (HLF) separated 3 weeks ago and somehow still think we are still together even though I clearly said to him everything that was on my mind. We still live together until I find an apartment. But I did something last night that I regret terribly. I went out dancing at the club with my sister and that guy kept looking at me, he was crazy attractive. His masculinity and the way he was cocky made me feel some type of way. I got up to him didn’t even talk and started kissing him. We french kissed that felt like a long time and I stopped and left without saying a single word. It felt hot at the time but since then I feel terrible. I didn’t say anything to my ex and I don’t want to hurt him at all. I felt like I disrespected him, I still live with him and sometimes he gets in those moods he can see that things changed but I think don’t want to admit to them. The other guy messaged me on facebook but I didn’t respond and deleted the message.