Is it normal to feel like this?

I met this guy a while back and I knew he only had one intention which was to hook up. But I made it clear to him that I only wanted to be friends but a couple of days ago I let that slip my mind and we hooked up. I didn't think I liked him, but after that it's questioning me. He hasn't talked to me much lately and the plans that we've had for a pretty long time he canceled. I feel lonely like I lost a friend, but we weren't that good of friends in the first place. So now I'm just wondering what happened to make this happen besides us hoking up.