Mental illness while pregnant

I'm well aware some people are against people seeking mental help and possible medication so please don't reinform me. I was diagnosed with bi-polar at the age of 12. I'm currently 23. I've been on and off medication, hospitized once and in and out of treatment. My situation now is different than my issues growing up and I have a wonderful 2 yr old son and a daughter on the way and have decided I needed to seek treatment again to keep me healthy for my children. Though I am undecided on when or if I should get back on medication if need be because I do plan to breastfeed my daughter. So I am curious as to what your thoughts were about medication while pregnant or breastfeeding. I'm asking this question to try to learn about it so if you have actual knowledge/ education of this topic pleaseeee comment, I'm wanting to be as informed as possible.