Feelings or no??

I went out with this guy for a very short time last year and I broke up with him as I just wasn't ready for a relationship.

Now he's single again after a long relationship with his girlfriend after me and we're getting close again.

He has been flirting with me and I have to and I've told him I'm still not ready for a relationship, as it just came up in conversation. But at a party I previously had, a girl, that I've recently become friends with again, starts kissing him and I automatically feel super jealous and I did get upset.

And that night he kissed me and we slept in the same bed all night, whilst cuddling. I enjoyed it and I like his company however I don't want to pursue a relationship with him..so why am I feeling this jealousy?? Am I being in denial to my true feelings? I need help because I am so confused and it hurts.