I applaud your ability to work those amount of hours and take that many credit hours, especially while doing it without meds. I've got AD/HD and a gamut of other issues, and don't know where I would be if I weren't on meds. I'm a non-traditional student as well, and I've got a 3.4 GPA in my major, but because of my issues I can only manage 6-9 credit hours, and that's with me not working!

What do you think it is that keeps you from excelling any further? You said you hardly put any effort into school, so it doesn't sound like the amount of hours you work or credits you take, is the factor that is keeping you from succeeding. Do you just like to party a lot, or do you possibly find the class work boring? The fact that you can pull a 3.3 without even trying, suggests that you are bright and possibly just not challenged enough to keep your interest.