I (20F) was a rebound in my relationship with (22M). How do I continue on?
For backstory, me and him met when I was 18 and he was 20. I fell in love with him quick, and he told me he had an ex he was still in love with. Me, being dumb, stayed. He told his best friend 6 months into our relationship he loved her and rejected me when I told him I love you the first time, called me her name, and prioritized letting her flirt with him over my happiness. I got so stressed I developed kidney stones and got really sick; I dropped to 80lbs. He had hidden pictures of her in his end table. That's the worst of what's happened.
Now, he swears it was all platonic and he lied for attention. He swears they never dated, he never even liked her, and I'm his first girlfriend and first love. But I can't get over what he did. I love him, and I won't leave him. I am however struggling to forgive and forget what he did to me, and struggling to stop hating myself for staying. How do I move on? What am I doing that isn't right? I'm in therapy, I'm on medication, I've been journaling, I've been doing self help, I've even dug into retroactive jealousy because I cannot handle him having an ex girlfriend at all for personal values (I know, one and done relationship is impossibly rare, but it's still hard to come to terms with the fact I'll never be someone's first and only love) but no matter how hard I try, nothing is getting better. Am I doomed?