I am sorry that you are feeling really down. Unfortunetly, depression is one of the parts of bilopar disorder; it is also one of the hardest parts to deal with. It is not something to easily shake of, and a lot of people in the board have been there.
Hang in there and know we are here for you if you need to post how you feel. Sometimes that helps one feel a little better.
I am glad you are going to your pdoc for help, it is not something that should be ignored. They don't always change your meds completely. They sometimes raise your dose of your current meds, add a new one to the existing one or in extreme cases change your meds completely. Please let us know how you are doing and how your appointment goes.