well...I can relate to you very well....but my finding is that mostly my jealousy is true feeling and there is a reason behind it...."I don't feel secure in the relationship and that's because I don't get enough love, support and attention from the other end!".....If you feel secure in the relationship and know that he wants you, then you won't care....
my last relationship has ruined mostly because of my jealousy and suspicious, but now that I look back, I was right....The same way that he approaches me, he did with this new girl....very easily he moved on....so...that's who he is...and I was afraid to get hurt, but I got hurt at the end....
I'm certainly sure now that I wasn't jealous, it was just not receiving the love and attention from him....and feeling that he's still looking for somebody else....and I was right....because he did what he wanted to do....
I've been in relationship that I was jealous, but then when I saw his love and attention I found out my jealousy was not valid....
I suggest you to look at your inner gut and trust it....If you feel jealous and insecure, then that's not a right relationship to be in....
take care
Marjan