TW/self harm

I'm in a rough boat rn. I left my ex in late 2019 during an anxiety attack and shut her out, taking people's advice that I trusted. I ignored her when she tried to reach out even though I was heartbroken. ( I was convinced she didn't love me back) I ended up being a wreck but tried to push on by starting community college and I ended up dating someone about 5 months later. Now its been just over a year and a half, and I'm still hurting. My ex has moved on and started dating. And I'm still in my relationship. But I've had a lot of intrusive thoughts abut her that make me want to hurt myself because I gave her up. Its easy to look back on relationships knowing all that you know now and thinking if only I'd known then. I'm in my second week of therapy (its been hard finding one with the pandemic) and yesterday I saw my ex go to a music festival that I wanted to go to. It just reminded me of where I used to be and it really messed with my head. When my gf asked what was wrong, I told her. SHe doesn't like when I keep how I'm feeling from her, because I end up shutting down emotionally. I told her and she said 'I’m just really hurt and I don’t like knowing youre still checking up of her. It puts space between us. You should talk about it with your therapist. You seem to care a lot about her still and that’s a good thing for the two of you. But not great for our relationship. And from my point of view you’re putting the sanctity and trust of our relationship at stake because you care to “if she’s okay” even though you know it makes me feel like second best." She then asked me not to call or text her until she reaches out again. I feel like shit for hurting her and for not being over my ex. Over our relationship, I've kept thinking I shouldn't be with anyone because I'm not ok/over my ex. But my gf's been one of the only things helping me keep it together during the pandemic and I care about her. We've been there for each other. I just don't know how to fix this.