There are times in our lives when we need support from our loved ones and times when they need support from us. You need support at the moment and I am sure that your loved ones are happy to give it unconditionally.
Depression is a terrible illness, it puts you right at the edge of your tolerance level. I had clinical depression that started at age 19 and my GP told me I was too young to have it, that I had everything I could want and pull myself together. I felt like I was walking a tightrope over a black pit and madness was waiting for me to slip off. I got better when I accepted that it was an illness like any other that needed medication and time.
I agree with Sea Angler, not having an explanation or a diagnosis for what is happening to you is so difficult, the waiting and the anxiety is awful. I really feel for you and wish I could help you. I can only tell you what happened to me and can say that I recovered, I am a better person, I have a love of life that I never had before. Yes I have PD but at the moment I am active in making myself the best I can be with the set of symptoms I have.
Please try to understand that you are not a waste of space, you are a beautiful person who needs support at this time, you deserve it.