I agree with Alicia... there are safe anti-depressants you can take, so talk to your doctor.
I went through some pretty bad depression during and after my pregnancy. I was very excited to meet my son, but at the same time very depressed about it. I mostly just had a hard time wrapping my mind about the fact there was no going back. That my life was going to be different forever. On top of that, I didn't like where I was living, I was still in school, and I started questioning my relationship with my boyfriend. Somedays I really wanted to give up.
How I got through it was by focusing on bonding with my son. I read to him, planned his room and what things he still needed, talked and sung to him, picked out baby names, and just tried to get out of the house and not dwell on things. I also really looked forward to each doctors appointment. For me, it really did get easier as it went along. The more I felt pregnant, the more I loved it!
I'm not trying to scare you. but I would suggest getting back on your medication immediately after giving birth though. For me those first few months were totally overwhelming and I struggled to make it through. Having a baby was a lot more exhausting than I was expecting.
Good luck with everything, and
PM me if you need to talk!