A talk with your pdoc would probably be a good idea...

Since you really don't have a clear idea of what you need to do...I think a candid conversation with your supervisor is in order (not about the depression). Strickly about work performance and what you need to do to be on track.

If you feel you are in over your head...Is there some additional training that can be given...

You know if you take the steps necessary to get a clear idea and then do it...there would really be a reason let you go...don't you think?