[RT Wolf]

In my view, you've got a few major problems to tackle (if you do choose to go ahead and complete the degree).

1. Lack of motivation: I think taking a hobby or something similar may help. And like others have said, motivational audio programs and etc may help you become more motivated.
2. Not sure about the basics: This is the sorta stuff that you can only feel better about by going back to the basics. This will mean more work, but you can accomplish it fairly fast and the boost in confidence may help give you more motivation. Grab a few of your first and second year books, and start reading them, answer a few questions for every chapter (just to double check that you've got an understanding of it). If you get stuck, study more
3. Organization: If you haven't done so, Getting Things Done is a wonderful system for organizing the minutae and the higher-level stuff. Find out exactly what you want to do and how you want to do it.
4. Energy (this is sorta tied to motivation): See, the way I look at it is like this, if you have lots and lots of energy, you're expending less (percentage wise) of your energy on your current work. For example, say all your work requires an energy level of 10 and all you have is an energy level of 10, you'll feel stressed cause your work is taking up 100% of your energy. However, if you have an energy level of 100, then doing tasks that require an energy level of 10 are much easier to do.

There are many ways to improve your energy level including, waking up at the same time every day, excersizing regularly, eating properly (odn't have to go vegan, just eat well) and a few other similar things.

Good luck!

Edit:

For Organization, this quotation may help: "In any moment of decision the best thing you can do is the right thing, the next best thing is the wrong thing, and the worst thing you can do is nothing." by Roosevelt. What I'm getting at is that you may not know where to start, so just start at whatever. Flip a coin if you have to. Once you've committed yourself to a course of action, you'll feel better (committment tendancy, see sig).