'Usually', you can add another bird and regardless of whether they become friends or not, you won't lose your bond.
I had something unusual happen, and I'm still not quite sure what, but as Griffin became bonded to Raven, not just friends but bonded (both males), my once hand fed, completely tame, touchable all over, cuddly baby who loved me, became very weary of me to the point he literally freaks out with me at times like a parent raised bird who distrusts humans. Literally like a "switch" flips in his brain. At times when the "switch" is turned off so to speak, he will let me step him up but only if it's away from his cage, and may stay friendly for up to a few minutes before the switch flips again and he has to bolt away from me doing the screech of death.
I'm not saying this is by any means normal or usual of what happens when a bird bonds strongly to another bird, but it's only my experience. I hope he outgrows it someday, as sometimes it's as tricky as getting a wild bird back into his cage

. I have not had or heard of this happening another time to me or anyone.
My handfed English budgie lost most of her tameness when she started living with my American budgie who is wild. That's a different situation though. Mink will still step up sometimes, she just doesn't 'like' being handled.
My Griffin is just an unusual story, but "usually", if you have a bonded bird, they will not 'break up with you' and act like you've become a hideous ogre. I wouldn't worry about it happening.
Edit: I just read Sunblaze's post and I agree... if you can possibly wait until your baby is older would be best
