Overcoming depression and getting back on rails with PhD work
Depression is very common amongst graduate students and faculty. So know that you are not alone. 


  About 60% of graduate students said that they felt overwhelmed, exhausted, hopeless, sad, or depressed nearly all the time. One in 10 said they had contemplated suicide in the previous year. --  AAS Science Careers


However, there is very little that the community on SE can do to help you. We are not therapists and cannot provide a therapeutic relationship.

Know that there is no shame in seeking help. Your university almost always has a mental health clinic with free or subsidized service. Whether you prefer talk therapy or psychopharmaceuticals (or both) is up to you and your insurance plan -- but please do go seek help from specialists.