I want to go another tack here...
He is now interested in a girl, who I find myself extremely attracted to, but also who I see as a potential great close friend. I seem to be having a huge problem with him wanting her now that I am starting to get to know her better. They haven't done anything more than flirt, but even the thought of them together makes me feel ill and stressed.
*bolding added by me
I found the comment about the OP being very attracted to her boyfriends new gf a significant one... is it possible their is some dual jealousy happening here? jealous of both of them? is there a possibility that a triad could form out of this?
Just a question I felt needed to be thrown out there... certainly not something I would pursue until jealous feelings have been sorted to find their base reasons.