Everyone's different, but for me here is how my brain works -
I could be jealous if I was in a position where we broke up, I still had not moved on emotionally, or was still in a place where I still had no deep feelings for someone new. Once I do have feelings for someone new though, I have little or no feelings about an EX. Arguably I'm kind of black and white emotionally in that way, once I'm in, involved with someone, I'm very very involved, so that I'm almost entirely tuned out to other people, as well as EXes.
Okay so no point yet, just exploring where you're at (my telling you how my brain works is just a point of comparison).
SmileXx wrote:...
I dunno. I think I just wanted him to not date anyone else.
I don't like when people move on... I'm that way. I'd have the whole world after me in a perfect world.
Lol.
It just really bothers me that I care at all.
...
So this is a difference between how my mind/heart works and yours, and maybe key? I'm happy with having one person to romantically love, plus some occasional casual reminders that I'm desirable from others.
You've written here that (on some level) you wished everyone desired/wanted you. Just from a very superficial analysis then, one (of 7 billion people) that you had, got away. For a moment let's go with that idea -
Maybe it goes back to a simple thing. For some people their sense of value is bolstered by the quality of a few relationships (perhaps those types are also statistically the more introverted types who tend to prefer a few close relationships over many casual relationships?). For others their sense of value is bolstered by the quantity of relationships, even if that means quality of the individual relationships suffers some times*. What I mean by suffer some is that there can be a time/emotional/conflict-of-interest cost associated with juggling too many relationships, especially when there is conflict between the people one knows, and we are put in a position of needing to play mediator, or outright choose sides.
Anyway, just some thoughts to see if any of this rings some emotional bells.
*One related last comment, an example of how a relationship can suffer in your situation is that you have a new BF. There is a risk that your jealousy over an EX relationship could interfere, even significantly devalue him, causing your current relationship significant harm. I know for me, if the woman I'm with was having significant angst over an EX, I'd take it personally wondering why her heart is on him at all versus on us.