I'm in love with a boy who once loved me but I think he moved on. Now I just sit around waiting for him to realize that he should be with me
What makes you think that he will want to be with you again?
I gave him a golden opportunity and he rejected it, I think he's wasting his time with someone else
Maybe he really cares about the girl that he is with now. You should not risk finding happiness with someone else just because you are waiting on him. He may decide to never leave her.
He should be with me as I'm a better person, isn't that obvious?
It sounds foolish to wait for someone to love you who already left you in the past. It's not probable he's coming back.