I'm shooting more for psychological. First off, you admitted you're depressed. It sounds like your nerves are shot because you don't have the weed to fall back on, and this scares you. This has increased your floating anxiety, and because of this, you are having mild panic attacks and a sick stomach. These really are all symptoms of depression/anxiety. You were smoking so much weed before, you were probably self-medicating yourself. Now, you don't have the weed to calm you, and your depression/anxiety is running out of control.

You should really go to the doctor, period. Talk about everything, how you've secluded yourself, the death, and how you're life has been in the past. Don't be ashamed. Things happen, man. If someone wants to mock or scold you for this, then they're evil people. I think many people are depressed and self-medicate with all sorts of things (legal and illegal). This is normal because life is hard.

Whatever happens, don't let yourself go much longer without seeking some sort of professional help. If you don't have health insurance and/or the money, then try to find some free clinics in your city. There's places you can go.

Oh and also, try getting out of the house. Call friends. Go for walks. Just something to get you living again.