I've still unfortunately been hung-up on someone I never officially dated... for years.
That's way too long. Why would you still be seeking a relationship with him?
I don't know. I'm annoyed by the fact that he ignored me and keep me hanging around because he's already got his girlfriend...
It is not healthy to be obsessed with some one who is already in a relationship. You should move on and find someone else who is interested in you.
It's too late. I'm jealous of her because of the attention and the fact that he loves her more than me. I can't get over it!
Don't you think you deserve better than this mental burden you are putting onto yourself? How about trying to distract yourself with friends, or perhaps look for another fish in the sea. You might miss good opportunities if this keeps clouding your judgment.