I really like him, but I don’t really feel the “thing” – Need Some Advice

I need some help regarding my situation:

I’ve broken up with my ex about a month ago. I got tired of having to do all the work (calling, sending sms, asking for skype dates,…) and I felt my bf wasn’t really loving me, making so many plans but never anything really involving him. I broke up because I didn’t know what else to do. It was my last attempt to make him understand that his behavior wasn’t right. We got engaged last february, but I already broke up with him in April because we were having issue.

Now I’m dating a new guy. He’s a friend, I’ve known him since January when we were volunteering on a project together. He was pushing me to take a stand and do something with my bf. I kinda knew he wanted to date me but didn’t want to face it. Right after I broke up with my ex he asked me out. And I said yes because I didn’t want him to feel sad. I like him, and I thought maybe it would work. We have a lot in common and we have a similar way of thinking.

But I realized I don’t feel the same than I did with my ex. I really like him, but I don’t really feel the “thing”. For example, last night he called me while I was sleeping. It just made me angry because I was sleeping, I didn’t want to wake up and talk with him. But with my ex, even when he called me while I was sleeping, I still felt happy and wanted to talk to him even though it was late and I had to go to work in the next morning. I don’t feel jealous when my bf told me he’s seen some girls that were looking at him, but if my ex tells me he went to club then I’ll just imagine things and get jealous whenever I see a picture of him with another girl.

So I’m wondering: am I forcing myself in that relationship? I want a relationship that works, and with my ex it was very complicated because we were in a long distance relationship. And we’ve had issues in the past, and it’s difficult to imagine how we could be together in the future. With the new bf I think things will be much easier, but I’m scared I will still be thinking about my ex. What do you think I should do? Please, give me some mature advice.