Why is he doing this? Why is this happening?

I have known my best friend for three years now. I have also developed a very deep crush for him. He didn't have much friends when we first met, but he's starting to open up to others presently and I think it's a good thing and I'm happy for him. And I respect the new friends he's made because they happen to be my very good friends as well. Aside from this, I started flirting with him, ALOT. I really started to like him, ALOT. He rejected me in the past when I asked him out, but my feelings were still very strong. As I was unaware, my flirting started making him feel uncomfortable and I was soon taking advantage of our friendship. I soon lost his trust to a great extent. I felt really guilty about it all and wish I could take back all the things I ever did. It wasn't that bad though. Just a peck on the cheek and nuzzling. But it obviously made him feel uncomfortable. A few months p by with midterms and vacations and the tension seems to fade. Now, this one of my good friends in particular ( I'll let her be known as Mary because I don't wanna give out names) seemed to take my place as his usual company. And soon enough, the friendship between him and I weakened and the bond between them grew. Of course I felt jealous, I mean, wouldn't anyone? But I let it slide by. A few weeks p and he seemed to hang out with Mary almost all the time. His excuse for me, " It's a new semester, so we don't have that many cles anymore. If that's the case, how come I talk to so many others who I have only one cl with? Things got worse. I see Mary and him holding hands. He gives her daily mages on the shoulders. He rests his head on her shoulder.He nuzzles her in the hair. She always sits next to him. Not even a slight glance in my direction. This may seem shallow and envious of me, but, I'm a human with feelings too. One day after school, I see him literally her against a wall. And I wouldn't be complaining in the first place if they didn't do these things when i was literally standing right there. Is he doing this outta spite? for revenge? Or am I just overreacting? And plus, Mary is or, was a good friend to me as well. Is this **** really necessary???