<human>: I don't actually understand myself at all and am actually pretty ashamed of myself for still holding on to this loser of a guy I was with. All my friends and family can't understand why I'm not able to see him for what he was and move on.

Anyway, I did the worst thing possible, I lurked his instagram (first time in 2 months). It seems that he has been dating this girl only a month after we broke up. I looked on her page and there are all these photos them on dates to places he would take me and these sexy selfies she took of herself in her underwear lying in his bed.
Now I know how bad this is and how I really have done this to myself. But the deeds are done and after feeling like I was finally letting go, now I feel like I'm right back to square one. 
Yes our relationship was brief, but it was intensely passionate and we went through quite a lot. I had no choice but to break it off with him because it became so toxic and now I find that he has moved on so quickly, I just can't help but feel so pathetically disposable.

I haven't been able to think of another man since we broke up, let alone date another guy. I've tried to get back into dating but it only just makes me miss him more. This is what really gets me, he has left such an adversive impact on me and after everything we had gone through, he can just move onto someone else so quickly.

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<bot>: Has anyone experienced anything like this? Can anyone share some guidance as to how they managed to overcome this nauseating feeling of being so quickly replaced?