How to move on when u love ur ex but know he is not good for you?

I’ve been stuck in an emotional loop with my ex for months, and it’s slowly destroying my peace. We broke up long ago, but every time I try to move on, he comes back saying he’s depressed, can’t sleep, or keeps seeing me in his dreams. I end up feeling pity for him and comfort him, even though I know it pulls me back into the same cycle. I still see him at university, and watching him look miserable—messy, tired, and lost—makes me feel awful. I know I shouldn’t be responsible for his emotions anymore, yet I can’t stop feeling empathy and guilt. I feel like I ruined his confidence and hurt him, and that makes me want to take care of him again. At the same time, I’m also emotionally exhausted. I’ve lost motivation to study or work, I skip classes, and I don’t feel joy in anything I do. I used to have a fire in me to get better after our first breakup, but now that’s gone too. It feels like I’ve lost my sense of self. Even though I know this relationship can’t work—he’s immature, dependent on his family, and not ready for responsibility—I still miss him deeply. I still feel a lot for him and want him to be the man i always saw in him. I can’t stop imagining him with someone else, and it hurts me every time. Its hurts so bad. I want to stop caring, stop feeling this constant sadness, and start feeling normal again. I really wish he calls me and makes everything patched up. How do i move on from this state !?