Nah, its called work for a reason. If we liked it, it would be called play. At 20 you are still getting out of the school routine. My guess is that you just haven't found a job that you like. And its not a personality disorder - as I said its called work. I know a lot of people that survive work so they can have the weekend. Probably, the thing to work at is making work more interesting for you, and if that doesn't do it - than just accept it and have fun when you aren't working!
I don't know. It sounds like more than just an "I hate my job" kind of thing. There is the possibility you could have ADD. My boyfriend is 35 and he was just recently diagnosed with it. He's very motivated and enthusiastic about his work, but was feeling overwhelmed and forgetful everyday.
I'm kind of skeptical when it comes to the whole diagnosis of ADD and ADHD, especially in adults. It seems like doctors just try to have a drug and disease label for every little minor symptom or emotion that naturally occurs in life. But I do know they have to test you to diagnose you, so you may want to see a doctor. Another possibility could be depression, especially if you've had those feelings for more than 2 weeks. Depression can come and go naturally for all people, but the longer it lasts, the worse it gets without counseling or treatment. And those who have depression often experience it initially in their early 20's.
In the best-case scenario, maybe you just need to look for another job? Is it the hours you don't like? The people you work with? The type of work you do? Is there anything else going on in your life that could be causing stress and unhappiness? Maybe those are things to consider.
The last job I had I hated so much that I would come home crying at least once a week. Then I started another job, which requires me to work from home, and I'm not so sure I like the flexibility, because I can't seem to get motivated to get going everyday either. (Which is why I'm on here right now!) haha Sometimes, I think some jobs are just better suited to certain personality types and you have to figure out what works best for you! Of course, most of our ideal dream jobs are already taken, and you're always gonna have something you don't like about work, but as long as the positives in some way outweigh the negatives (less money, but more fun, or more money, but more hours,etc) you should be fine! Good Luck!
Having ADHD diagnosed at the age of 20; I know what you are saying. I would recommend sitting down with a physician.
Maybe you are in the wrong line of work. If you could chose any profession, what would it be?