I broke up with my ex-boyfriend because I didn't like him then but now might want him back?

This guy was absolutely in love with me and told me that himself, but back then I wasn't feeling the relationship and so to make sure I didn't lead him on for too long, I ended it after about two days. It felt weird for me and I knew that the feeling wouldn't go away so I decided to not fake feelings with him for so long and then end it. We stopped talking after that because of one little argument a few months later, and it stayed that way for a while.

I have a friend who I'm close with that talked to him for almost as long as I have, but always kept her distance because she knew there was something between us. Once that was over, about 5 months later she told me she thought that she liked him and if it made me uncomfortable in any way, I should tell her and I said it was fine, which was how I truly felt anyways. They begin dating and I see him for the first time in forever and it's like we're all friends again and its really fun. He ends up breaking up with her because he realized he wasn't interested in her like that but really wanted to be (IRONIC BECAUSE I FELT THE SAME I KNOW). Later on he told me that he didn't feel the same stuff he felt with her as he used to feel with me and I told him that was sweet, but that's all that happened.

They stop talking because she's mad at him for ending it and they just now started being friends again. He and I have stayed being friends throughout this whole thing like when we used to be friends. We all hung out 6 nights ago and it was really fun, but one thing I noticed was that he was all over ANOTHER one of my friends and holding her in front of both me and my friend. Everyone was confused but he is a very flirty person so we brushed it off. That night apparently, he asked a different friend of mine if it was obvious that he still liked me and she said it was very obvious which confuses me EVEN MORE. He made out with her at the party too. I don't know what feeling I got, if it was just weird or me being straight up jealous. But I think I do feel something for him, but it could never work out because of him dating my other friend..right? If I asked her she would say she's fine with it, but wouldn't be. But basically these are the questions going on in my mind:

Why would he be all over my friend if he was still into me?

Does me being jealous mean I have feelings for him?

This dude sounds like he's quite happy just going through one of your friends after another. Two of you down (how many more to go?)

Anyway: I think you're jealous not because you have feelings for him but rather because he wasn't doting on you. Its probably a matter of 'I don't want him but I don't want anyone else I know having him either.'

What ages are we talking about here? Sounds like typical teenage guy behavior. He's a jerk.