Why does he act so hot and cold?

I wrote a question a while back asking advice for my situation with the 43 year old man from my work.. Well since then we have “hooked” up a few times, he even spent the night at my house.. So I am faced with another dilema. I am having a hard time reading him. One minute he’ll be hot and want to spend the night and have amazing sex or just hang out with me, and the next we wont talk for 2 weeks. At first I just assumed this would be a one nighter but he calls and wants to get together at times. I would be lieing if I said I didn’t have feelings for him.. Do I love him??? I dont think I do right now. I think I am stopping my self from becoming to “in to” him for the sake of my own feelings. He is really fun to be around though, we have sooo many things in common and when we are together we dont always have sex. We can totally just hang out with one another and watch a movie or go for a walk. But he is like a big kid. He is very immature for his age and I think I am overly mature for my age (22) so in a way we balance eachother out pretty well… gosh, I think I can go on for days on this subject so I’ll just quit now… I hope this provided enough of a story for you to decipher and hopefully come up with a couple of pointers or advice for me.. Thank you!