Was he actually Jealous or pretending to be?

I had an ex-talking stage. Basically, it didn't work out and I changed my number. When we came to school we pretty much avoided each other. One day in class, I caught him staring and he looked away. And guess what I started catching feelings again. Before I get too deep I wanna give a brief description of his personality cause I feel like this can contribute to my question a lot. He has a high ego, he's manipulative and all-around a very terrible person. When I changed my number because He posted "his new girlfriend" he got mad at me and started dragging my name through the mud! He then broke up with her. He then started showing off in front of me, tryna make me "laugh" and I ignored it. His best friend would stare at me sometimes and when I mention a guy, he seems invested. The first time he actually started talking to me was a shock. He said a comment about me as if he was talking to me but I didn't answer at all. His friends were shocked that I didn't answer. And his best friend would tease the other girls about them being in love with him but not me. I continued my day and the rest of the week he tried calling me flirtatious names but I didn't engage and I pretended like he didn't exist. He would try to be where I am and always tryna get close to my friends. But you wanna know how he's started randomly acting like this out of the blue? It's because I was singing a love song in class one day passionately and he happened to see me. I feel like the only soul reason he started acting like this is that he didn't want me doing better or doing better without him. After I changed my number I started to better my self and I had a glow-up. Not to get back at him but to get back to myself. So I caught on. But here is the real reason I asked this question because I'm genuinely curious if he was. Our classmate was walking back to his desk and my desk for papers and he said out loud to the guy "What are you up and down for, relax". So was he actually or just pretending?
Was he actually Jealous or pretending to be?
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