10 year situationship

In college I had a short hot and heavy fling with a guy I met on the first day. He actively pursued me even when I turned him down. There were moments I could tell he had genuine feelings for me. He would express it to me and wrote songs about me. Then the next day he would act like he couldn’t stand me. We were never official and I broke things off and we didn’t speak for a year.

Then we reconnected and would catch up every few months as friends. Every time we’re both single we hook up (we’ve always had very intense good sex) and date semicasually. Then the hot cold stuff begins again and I usually pursue other suitors. We still exchange memes and stuff and every now and then he’ll try to flirt or see me. Even when he has a long term girlfriend which I decline.

He once admitted he loved me but only when he found out I was in a relationship. I realize that this is most likely a fboy who’s just not that into me, but 10 years is a long time to keep this up. I’ve never gotten the full story from him and I’m curious if anyone has any insight?

TL/DR: Guy goes super hot and super cold on me intermittently for 10 years. Why?