Did you do a tag search for 'jealousy'? There's oodles of great threads about it here.
Have you considered therapy?
I'm not much use other than that, as I'm the one being shared.
Love is that condition in which the happiness of another person is essential to your own...
Robert A. Heinlein
Me: female, bi, (formerly hinge of a vee)
with FirstBoyFriend (FBF)(moderately long-distance)
and no longer with CurrentBoyFriend (CBF)(who lives in the apartment building next door)