Babysteps, I am sorry this is all so confusing for you and you are very correct to say that a lot of mental illness have similar symptoms. I am not a psychiatrist so I wont diagnose you but in my case I am Bi Polar and chronic severe depression is a symptom of that, I get severe anxiety as a result of the Bi Polar and I used to avoid people as I was so embarrassed by my illness and consequently isolated myself when both depressed and stable.
I get very long severe depressions that do not react sufficently well to standard anti depressant therapy so I have had 3 courses of ECT to date. I cannot speak for anyone but myself when I say i found it very effective and quite quick to alleviate the depression, the only initial side effect was a blurring of my short term memory and a slight headache but both went away after a while. I would sooner get ECT now than wait to see if an anti depressant works after 3 / 4 weeks which it invariably hasnt for me in the past.
If you need any information or have questions about it by all means please PM me.
Thanks