I've found that the stress of earning a degree can indeed trigger all sorts of issues--including feelings of worthlessness (of all things!) that of not feeling worthy and of being a fraud because others "don't really know" you etc... but on the end, whatever feelings triggered, it often results in depression.
You do sound depressed, and I would hope that you would keep your ties here at PC.

There's no reason not to, as I have done as well, kept my account.
You know, I trust, that making decisions while depressed isn't a good thing. When we're numb or empty, well, we wouldn't want anyone we know to make a decision at that time---so please wait until you feel better to decide, ok? I'm sure there are some members here that rely upon your words, even though you may not know them.
If you're looking for enjoyment here... what have you joined? Chat? The game arcade? A social group of your hobbies? (I welcome all competitors to the game arcade hehehe.)
Even if you need to take a break, do so, but come back okay? There are people here who care about you.