My ex gets bothered and upset when I talk about this guy?

My ex broke up with me 10 weeks after going out. While I thought everything was going smoothly, he thought differently and broke up with me. He thought he was making me unhappy (not true) and parted ways with me. I thought this break up could be negotiable and we could make compromises. I didn't think it was necessary to break up completely, but a break did seem mandatory. But he said no, he didn't want to deal with a relationship. We're exes but we talk on a daily basis. I met this new guy earlier last month and now I like him. I've never told my ex that I liked him but I caught myself occasionally bringing him up to my ex, and he'd get really heated and bothered. However, my ex doesn't want me anymore? I still have feelings for him too. I'm just uneasy about the whole situation. Advice?