Explain this male behaviour?

I really like this guy and we were friends, he told me a few times (really out of the blue) that he wanted me, had feelings etc. BUT, this is the prob, I didn't believe him cause he flirts with every other woman bar me. Now I accept that I don't act flirty to him, but that's cause I genuinely care about him (have told him how I felt). This has gone on for years. We are like two strangers and a lot of that is down to me and not understanding why he is soo chatty and complimentary to everyone bar me. He showed off his grandchild to all these beautiful women but never even mentioned it to me and when I said it to him he blushed. He talks to these women, sits with them at nights out, even flirts with them in front of me. Yet, he looked at me most of the night and always tried to get with me. Now things are very strained between us, we hardly talk, he acts funny around me and looks away or down when we p as he says hello. He gets angry and hurt though if I act like he is just someone I know. Why?