teen drama

(Ex) boyfriend broke up with me a while ago, he said he no longer had feelings, but we still remained friends and nothing's really awkward between us being friends. 
I still have feelings for him, but if he doesn't have feelings for me anymore then nothing is going to happen between us, so I thought it would be best for me to move on. He already did a couple days after the breakup, since he told me he had a crush on this girl we have a class together with, but told me he doesn't like her anymore.
I've already had multiple guys hit on me, but I have denied their offers of dates, sex, etc.
Their is one guy who I have taken a liking too (a friend of mine), but it is a guy that my ex didn't like while we were dating, because he was very suspicious of him. 
I've just been talking to him, because he's been helping me and talking to me to make me feel better about the breakup. But when my ex sees me talking to him, my ex goes up to me sounding mad and ask why I'm talking to him.
He says he doesn't like him and feels jealous and upset when I'm around him, and I don't understand why since he says he lost feelings for me for a while now. My ex doesn't even want me to mention or talk about the guy when I'm around him.
I'm just confused right now. Does my ex still have feelings? And do I keep talking to the guy or don't, out of respect?