Hey there Keenie!
I actually received my bipolar diagnosis when my son was 3 1/2. I had a horrible pregnancy and I would get so angry when I saw pregnant women just falling all over themselves to talk about how WONDERFUL their pregnancy was and how EXCITED they were to have a child. Then I felt like a monster because I just wished I WASN'T pregnant the whole time.
I had my son and I just absolutely crashed. I hated every second of my life. I couldn't feel any love or excitement towards him and I just hated being left alone with him. I never hurt him, thank goodness I never had the urges to, but I would just stare at him and wonder how I was going to do this for so many more years. I had suicidal thoughts daily. I wanted to leave the baby with my husband and my family and just get in the car and drive away forever. I went to the doctor and he told me I was "textbook postpartum", put me on Effexor XR and let me go. The meds did nothing. No other anti-depressant did anything either.
The suicidal tendencies got worse, even as he grew older. This year I went back to the doctor, she listened to me for like...TEN minutes, then asked me if I had ever been diagnosed as bipolar. I am finally on meds that are helping. I can play with my son and laugh with him, MOST of the time, and I feel stable a good portion of the time. But my doctor told me there is a 30% chance he will end up with the same. That terrifies me. Me PERSONALLY, I would not have a kid if I could go back and do it all again. My in-laws bug me about not having any more kids, but I have put my foot down. If my son DOES end up bipolar, I can concentrate on him and his mental health as much as possible. I am not sure if I could do that if I had multiple children.
This is just me though. Everyone has a different view on it. I know it is a hard decision, so I wish you and your husband all the luck in the world making a choice.