Am I a red flag that I don’t have any friends?

Basically, was in a group of 26 in first and second year of uni and although I haven’t been excluded from the group, I realised they weren’t actually friends and they weren’t my people. One of the guys was bullying me last and they all ignored what was going on and wouldn’t help me or even help to resolve it, he also started spreading rumours about me and they sided with him and started blanking me so I blanked them. I thought I got on ok with some of the girls but they stopped speaking to me over the summer break and now that it’s uni again they’re talking to me but only when we have a lecture together. I was quite outspoken about what he was doing to me and I feel that therefore maybe I’m just not the same as them, not on their wavelength. I’ve hung out with them recently and I just didn’t feel good or that I was enjoying it when I was there so I’ve decided to stop seeing them completely. I now pretty much have no friends at uni and only have coursemates to talk to but again they only talk to me when it’s to do with work. I used to message my girl mates all the time but it took me a while to realise that they would take days and weeks to reply to me and tbh people are always on their phone today so if they wanted to talk to me they would’ve replied sooner.

I have 4 close friends at home that I hang out with, not in a group but I see them separately.

I’m in third year btw.

Would this be a red flag for a guy if he was seeing me? Am I the problem here? I’m also very shy and slightly autistic and overall not great in human interaction so I don’t really put myself out there to make friends.