Why is he behaving like a jerk? He is the one that had a gf.?

This guy at work helped me out when I moved to the city from another state. He took me out and was a good friend. I was going over a breakup and was alone in the city. We were friends and messed around one night. Well we stayed friends since we work together and did not know all along he had a gf. I told him once that if he had a gf we would never get together. That I do not settle being number 2. Well I found out he had a gf. On his FB he had all pictures of his gf together. He swore that she was his ex and they had know each other since 10th grade and he is now 33. They are only friends and I questioned why he had all the pictures of her and him. No kissing pictures but that they were hanging out. So I let it go. Well finally i told him that I just wanted to be platonic friends. We had never had so I thought it would be OK. He did not like it. He was furious. He became mean to me. Since we work together I thought we can be professional. He was not very happy with me. I told him we can be platonic and that we can be just friends. That I have a lot of male friends. He snapped at me and said that I have more guy friends. He has been such a jerk. We work together and I am sad this all happened. I thought he was a good guy, but I guess not. He wants me to quit my job which the job market is not good. I have been looking. why be a jerk. he is with someone else. I am still on my own and am starting to go out to meet people which irritates him. I just want peace.