Feeling used

A few months ago, I was talking to this guy who really really liked me, and I got with him a few times but i never liked him back and so ended the whole thing after a few weeks. Just recently we started talking again and I actually really liked him this time, and he told me he still had feelings for me, and he kept trying to make so much effort with me, so I met up with him a couple of times and then he asked me to stay at his on Halloween. I did, and we had sex, and then he didn't speak to me. He text me saying he didn't use me even though that's what it looks like, but that he can't explain what's going on. Then he posted a picture of himself in bed with another girl on social media. I feel stupid and used, and, embarrassingly, I'm actually very upset. anyone got any advice on how to get over this/pick myself up? It would be greatly appreciated 😔