What redpepper said, times a thousand. Please submit to your brain for consideration: It's more than possible that your mother is wrong. Being a mother (or an egg donor) does not convey god-like 'right' status. She's a human being, and sounds like a perfectly fallible one at that.
If your fiancee doesn't want anything to with you, why is he your fiancee? Keep reading here, there are as many ways to do poly as there are people (and probably more).
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 now lives in a house far away-with stairs I can't climb)