agree with jerrymichele....besides, I want to add something...if next time, she said that he loves her not you....then your respond should be..."wow...then why he's with me while he has a child with you! If he really wants you, he will find a way to have you back rather than you being a single mother"....
I'm so jealous in the relationship too and that's the worse thing ever....but I found out my jealousy is valid most of the time, because the guy is not doing it right....I think if such a thing is bothering you this much, then you will have so much problem ahead of you....do you really want to stay in a relationship like this?
Is there anyway that you don't see her at all? you can discuss this with your boyfriend and tell him that it bothers you and besides you don't need to intract with her at all....He got to agree with that at least....

take care
Marjan