Been two months since I was blindsided/potentially cheated on, just don’t know what to do.

This isn’t my first posting here, posted here about a month ago. Basically was dating this girl for two years and things were great between us. It’s always be on my bucket list to see the northern lights so for our two year anniversary we went to Iceland together and talked about our future and everytging. A couple days after the trip out of nowhere she jusr calls me and breaks up with me. No warning, no chance to fight for her, no chance to change just a two minute phone call and it was over. We’re long distance so I immediately drove four hours to her house and waited outside and she still wouldn’t talk to me or give me any kind of explanation or closure. After about a month of pure depression and grieving one of her friends (who I don’t know and have never heard of) told me starting dating someone new immediately after our breakup. Which naturally set me into a spiral, so I texted one of our “mutual” friends (her best friends fiancé so not actually neutral but we’d always gotten along) and just asked him if there was any truth to it. He said there was and it actually started before while we were in Iceland, which unfortunately lines up because she refused to let me use her phone or even for directions in Iceland and was very secretive of it. So that made me text her, she claimed we’d been drifting apart and she didn’t wanna bring it up and wanted to make me think everything was ok so we could get through the Iceland trip which was already paid for. When I asked her ab what her friends had said she called me crazy and paranoid, then told me that she told our mutual friend to tell me that to make me angry so I gave up which of her friends lied to me and there was no one new and there was no cheating. I don’t know what to believe. So I believed the cheating, cause it hurt a lot more but it made it easier to get over her. And I kept saying I hate her, and I keep telling people that. But I jusr can’t get over her and I don’t know what to do. Then recently I got a really bad concussion, which they tell you to lock yourself in a dark room with your thoughts, so that’s super fun. And because of the concussion I started hallucinating people talking to me, specifically her and in one of my hallucinations she said she was sorry and wanted me back and I almost jumped out of bed to go text her. We’ve still been no contact since I found out she might’ve cheated on me, and I know she’ll never give me an answer on whether or not she did, but I also know that if she apologized id go back without any question. And that really sucks, and I don’t know what to do.