OP, I think you should get to a doctors quicksmart and inform the university of everything you've just told us.
What you are suffering from is definitely depression, from what I can see. A lot of what you just described is exactly what I suffered from before I left university for a year. The avoiding tasks/fear of trying thing is exactly what I experienced. You description is probably the closest I've come across on this website, in fact.
It was those "exceptional circumstances" that allowed me to return without consequences.
However, I have to say, you might have a couple of problems 'convincing' the university. I'm sure it will be ok in the end, after medical assessment, but they will find it a little strange that you never went to the doctors to talk about this over two years.
If they are going to let you back into uni you also need to prove that you've sought help for your problem and are tackling it. i.e. I needed to take medication and see a counsellor for a while, then get a medical certificate saying I was fit for university after my time off.
Anyway, I have a lot of sympathy for you and I hope it works out.