It might not be the right time to take It on... But ...
Just to say you can do it! I have three kids, single parent, went through college twice ( yes I know, no PhD ) but all the same. It was hard and I didn't have help from family or anyone. I was also unmedicated. And I'm not exactly the strongest person around. I did end up graduating with a 4.0 which allowed me not to have to pay back all my loans.

Just don't sell yourself short because of Bipolar or any other circumstances, because we have an amazing way of overcoming odds. Timing might not be great at the moment. But what's the rush, you know. If you had to put this off for now, there is no saying you cannot have it in the future.

I hope you start feeling better soon, mixed episodes are the worst indeed. Dont put off calling your pdoc any longer. The sooner you make the call the sooner you might get back on track.