What the hell am I doing here? I don't belong here

I couldn't get to sleep last night until 3am and my exhaustion this morning brought back memories of when I was addicted to IRC and sleepwalked through a semester of undergrad. My favourite memories of that time are of how heavenly it felt to close my eyes or put my head down on the desk for five minute breaks in classes. In any case, I need to get to sleep earlier tonight but it's 9pm and I'm still in the lab. I haven't done anything productive since 6pm so why am I still here?
There was a lot I should've done today - a whole heap of reagents arrived so I should've set up an experiment with them, I needed to grow bacteria, analyse data, write my proposal (even thinking about my proposal would be a start) but I didn't do anything (except get my minesweeper time down another couple of seconds). I keep thinking I'll snap out of this and go back to my normal level of procrastination that still allowed me to get things done occasionally, but I just keep getting worse.
I read an interesting entry on 43 folders the other day: "Try looking at your mind as a wayward puppy that you are trying to paper train. You don’t drop-kick a puppy into the neighbor’s yard every time it piddles on the floor. You just keep bringing it back to the newspaper." My mind feels exactly like a wayward puppy at the moment but I can't seem to even manage the objectivity to metaphorically get the puppy's attention, let alone make it do something it doesn't want to do (ie my thesis proposal).
The closer the deadline gets the more anxious I get, but instead of doing something about it I just avoid thinking about it so I don't have a panic attack. I'm terrified that my advisor will ask for a draft any day now and I have nothing more than section headings to show. What I'm really scared of, though, is that he'll find out that I really don't belong here... There's another student in the lab at the moment and I'm scared of him too. He already seems to know what he's doing but I feel completely clueless still.
I actually went to a seminar on "the Imposter Syndrome" a couple of months ago. Apparently it's not just me who feels like I'm going to be found out, but the seminar wasn't very helpful. I still feel like everyone else just feels like that for no reason but I really don't belong here. It's not just here, though. Even at my home university which is far below Prestigious University standards, I felt like I shouldn't be in the lab I was in. That made for some fun guilty feelings when I got in here and all the people who deserved it more were staying on there...
I feel like I need to write some kind of conclusion to finish off the post, but I don't have one. These ideas aren't going anywhere, unfortunately.