Am I still jealous of my ex? Or do i just hate his new girlfriend?

Im 16 and have a boyfriend I am so so happy with .. BUT everytime I see my ex boyfriend post pictures of him and his new girlfriend (a girl he cheated on me with, hence the reason we broke up), I dont get jealous, I just feel sick and it puts me into a really bad mood. I still care about him as we were such close friends before we were together but I dont love him anymore so I dont understand why I'm feeling like this?  My new boyfriend is my world we rarely ever argue, he does absolutely anything and everything for me and I couldnt be happier - so someone please help me to understand why its bothering me?