One of the options that many bipolar patients explore during pregnancy is ECT. If you're having episodes, and are concerned about taking meds, ECT may be right for you. It works immediately, no long wait for the meds to kick in, and from what I've read, there are less safety issues for the baby. What has your OB/GYN said regarding the meds? If she/he has issues with the meds then a chat with your pdoc might be in order.

Best of luck and congratulations on your baby boy!