Ex got into a rebound and I'm still struggling

My ex and I broke up about a month and a half ago. I voiced my concerns about a guy that came between us and she made it clear through her actions that I couldn't continue the relationship. They were already doing love hearts and giving each other compliments within 2 days of breaking up. Recently, I found out they got together. They share so many more interests than we did, however this guy is much older than her (shes 19 and he's 27). Shes only posted and tagged him on her motorbike account with helmets on that a lot of her friends don't even know about. I've been in therapy and going to the gym, but I'm still checking her profiles multiple times a day. I miss her a lot. We were each other's first everything. If she came back and apologised for the things she did and truly wanted to change and be better I would take her back but I don't know of she ever will. I sacrificed so much for her and did so many things that most guys wouldn't do. I can't even picture myself with anyone else or imagine myself dating anytime soon.

Has anyone else been in a similar position? Could you share your perspective and what happened? Any help would be greatly appreciated 🙏