Am I the side chick??? Please help

Okay so I've known this guy for over 4 years. At the time I really wasn't interested in him, he was just always annoying but I never understood why. Turns out he always teased me because he had a crush on me. Didn't know they still did this in HS. Anyways not too long ago we got really close and he would always display his feelings to me and at the moment I didn't know how to feel. Somewhere inside of me I really liked him and cared for him but I wasn't ready to date. But I still wanted to be with him but I was scared it would've been my first relationship. When I say I caught feelings and hard I did, but I pushed him away and hated myself because he replaced me. I pushed him away bc I wanted to see if he'd stay. Apparently I was easily replaceable. We eventually go in a huge fight and I plan to never speak to him again it was like 6 months later and I still wasn't over him but I was still pissed. He found his way back to me and we were on again not actually bf and gf but we treated each other like it. And I loved the feeling even if it really wasn't love it felt so good it was my little forever and I finally told him how I felt. I gave up something new I was starting for him and next thing I know he jumps in another relationship. I was so upset I said something I regret but I didn't actually tell him to his face but I felt mislead and betrayed. I thought we were on the same page. I see their pictures everywhere it hurts like hell. So we stop talking for a month or two and he comes back to see why I stop talking and calling he is still in a relationship but he told me their just chilling and he doesn't see her being the girl he marries and I started to see everything I chose for my future his future plans started to look like mines. Like I said I wanted to have kids at a certain age now he does. It was as if he was sugar coating that I should wait for him. Then one night I get a call asking about love and my views on it and if I ever loved someone if so who. Like he wanted to see if I loved him or something. He would call me during the day but this one came at night. I don't talk to him as much because he's in a relationship and I feel like if he really did love me why would he have left and why is he in a relationship with someone else/ he doesn't see himself with.