i dont have friends(sorry im just venting)

So i recently lost my best friends because they got tired of me being depressed cause it made them feel drained and stuff and ig they just didn't want to deal with me anymore, even tho I was always there for them whenever they needed anything and I would always ask if they were ok when they seemed down. They always acted like i was causing problems making me look like the bad person. They never realized their own mistakes but instead blamed everything on me. I was the one always apologizing or asking if they were ok. It just hurts cause I cared sm about them but they didn't care as much about me and never understood my feelings or cared enough to be there for me.
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The thing is, im going into my senior yr with no friends and no one to hang with at lunch or break ya kno
so ig i just need advice on how to make more friends when everyone is in their friend groups already
And for those who went through similar things how did you deal with it? How do you stay positive and stuff