Can someone help me pleaseee???!!!! (Very long but I really need help please)

Ok so I had this friend, Alexis, my she, my boyfriend, and I were kinda all in the same friend group until suddenly everyone in that group but my boyfriend stopped talking to me and stopped inviting me to their parties n shit. I thought that was super weird and I was really hurt about it, like I was friends with those people since 5th grade (I’m going into 10th next year just so you have a relative timeline) so I was super hurt that like they weren’t inviting me but they were inviting my boyfriend + telling him not to tell me that they were even having a party... and that Alexis girl and I have birthdays like 3 days apart, so she told my boyfriend that if I asked him to come over when she was having her party that he had to go to her party, she broke it down to the fact that 3 years ago he went to mine instead of hers because they overlapped (let me also add 3 years ago was the last time I had a birthday party, I’m not and fucking child anymore but she consistently had parties every year which he went to before he and I were dating) anyways he said sure because why tf not, he was gonna tell me anyways. So I brushed the whole ordeal off but I was still hurt, like I’ve been friends with this girl since 5th grade yknow? Anyways skip ahead a few months, were in class and I can’t sit next to my boyfriend because I hurt my knee and couldn’t sit on the risers in chorus class and had to sit in a chair on the side. I look over and she is basically sitting on top of him! I’m talking like basically in his lap! Which I could see wasn’t my boyfriends fault because he couldn’t move as there was someone right next to him not letting him move away, but this bitch had a whole 2 feet to move away! Plus she was like textbook flirting, the smiling and giggling and the playful shoves, and the constantly touching his leg or arm shit! I’m just trying to do some math homework, but any time I try to get my boyfriends attention to help me on a question which I’m stuck on she like basically forced him to look back at her. Any time he’d look at me she’d grab him in the shoulder and start talking to him. And see at this point I’m pissed and I feel hurt and betrayed, but I couldn’t do shit about it because I’m fucking crippled and can’t talk over there on my dang crutches. So I send my friend over to get him for me but he never comes he sits there while she flirts with him! At this point I’m balling my god damn eyes out and she doesn’t let him look away for even a second to see that! After class when I’m able to actually fucking talk to her I tell her “Back the fuck off my boyfriend” and I walk away leaving him behind because I’m pissed off! Later that day I hear her ass talking shit on me so I tell her “keep my name out of your fucking mouth before you wish you didn’t have a mouth” and as soon as she walks away I sit on the floor, crying, again. Like I just want her to stop going at my boyfriend! Anyways after school I got home and I see her and that entire friend group I’ve been in for 5-7 years has posted shit on Snapchat and Instagram. I call my boyfriend crying my goddamn eyes out and send him pictures of what they’re posting and he tells me to block them. He also tells me he won’t talk to them anymore because he “doesn’t want to be friends with people like that”. Skip to a few months later/ present time, he’s defending her saying she wasn’t flirting with him and she was never touching him and they were only sitting so close because they were being forced together by the people next to them, which is bullshit because she had 2 FUCKING FEET between her and the person beside her. And he’s friend with that whole group again, even sat with them during class instead of me. And they’re still being assholes to me, I just don’t know how to deal with this. Like it always comes up and every time it turns into a fight. Like I don’t know what to say, I try to tell him how I feel and he shoots me down or gets pissed at me. It’s always this same stupid fight! I just can’t keep doing this! I’m done fighting over this but I don’t want to make him choose me or them, because I know who he should choose and so does he but I’m not so sure who he actually will choose. He always says that he’d choose me but is always defending them and whenever he says that he won’t be friends with them it seems like he’s trying to guilt trip me into apologizing and telling him it’s fine to be friends with these people who have been bullying me all year just because this bitch wanted to get with my boyfriend... I don’t know what to do! Please someone help me!