FOMO and third wheel for the first time

I started high school 3 days ago and it's my very first year and on the first day I met this girl. She seemed super nice and chill and we are lunch together for two days. I thought I found a real friend but on the third day she brought another girl. I thought that we would all be friends but my first friend was a completely different person. They both talk to me less and are always laughing at jokes they don't tell me. I feel like a third wheel. The two of them have every single class together and I have none with either. They seem like they hit it off from day one and I haven't. They still text me and ask if I'm coming to lunch with them and they call me their friend, but I feel it less everyday. They keep getting closer and i'm drifting farther. I wanna eat lunch with another friend I have who treats me like a real friend but they always say that anybody who doesnt like them and doesn't wanna eat with them can screw off, and that they don't care if that person is friends with them or not. I don't want to say that i dont like them and that they are not my friends I just wanna hang out with new people. It's kinda been getting me down lately cause I've never been through this before. I don't know what to say to them.