There's a guy at school that hates the shit out of me. He isn't a typical 'alpha chad'. He's skinny, ugly, and unathletic, but he's popular and assertive. A specific example happened just now:

The situation: at a volunteering club before school. In it is me, like 4 girls, and another guy. This guy walks in late, like when there is 15 minutes left at the meeting, sits down, starts talking to everyone and making them laugh. At first he really ignores me and talks to everyone but me. Then he takes a few subtle digs at me. For example (I don't remember all of them, but here's some):

Girl: hellsward1 is our boi

Him: Really? (Smirking and raising his eyebrows).

And

Another Girl: talking about a gc we're both in

Him: Add me. Who's in the gc?

Her: lists some people, then says me and hellsward1.

Him: looks at me never mind then

Finally, he just stands up. And he's says to the girls, 'come on, let's go to the library' again ignoring me.

One of the girls is just like, 'no, I want to stay and talk to hellsward1'. I'm 90 percent sure she did it because she's sorry for me, because she hasn't been giving me IOIs or anything.

I'm kinda pissed. I've been working a lot on self-improvement recently, including lifting fucking hard, and this skinny asshole casually digs into me all the time. And a girl had to defend me. He's far more popular, charismatic, and assertive than I. How do I fix this?