Coming out to my friends

So this year me resolution was to come out to my family, friends, and fiance. I came out to my friends a little while ago, and they were all like, "Oh okay." Score one for me right?
Well my fiance got pregnant. Now I am happy about that, however she is not at all a lesbian, and I am about 99.9999999999999% sure that if I told her she would leave me and take my child.
I grew up without a father, and I would damned if I would abandon my own child, but this has been eating at me since we started dating. I would love to raise my child with the ideals of complete acceptance. I mean dream scenario: I tell my fiance, she accepts me completely, I go through transition, and we raise our child in a loving two mother home. However I doubt that would happen. I brought up an idea like. "What if our daughter is gay?" and she was like, "Well once she is 18 she can do what she wants, but until then she better bring a boy home."
I guess I'm worried about just how much she loves me.
Sorry to digress btw.
Anyway onto my parents.
My Stepfather can go shove a pipe up his backside for all I care (I highly doubt he would accept me), my twin is a prick, my little brother probably wont care, my mother is super catholic, but as her first born she has that immense love for me, my little sister would probably be ecstatic to finally have a sister. I am my little sister's role model. She want to be a musician just like me, and loves the everblazing hell out of me, with those those feeling reciprocated. I just don't want it all to blow up on me.

ANY ADVICE?
P.S sorry about my incessant ranting.

 

Thanks for the advice. However to be perfectly fair, I started dating before I even accepted being trans. I kinda screwed myself over.