You're not good at math because you haven't practiced!
PAT and Math need practice. You wont see the results in a day or two or even a week or two. Do a Math test every day, what ever you're struggling on in Math: Don't just look at the answer!! Understand the concept, watch Chad's videos (highly recommend if you have a weak background in math, I even did his QR quizzes) about that concept, and then watch Khan Academy if you still don't understand. Do this for even small things. At one point I was watching videos on calculating the least common multiple which I'm pretty sure is taught to middle schoolers, but I still managed to not remember how to find it. I would sometimes watch Khan Academy videos for an hour on just one topic if I consistently kept getting it wrong.
For PAT, it's just like everyone says: practice, practice, then practice. When I did those practice tests, I spent the normal 60 min doing them, then I would spent like two hours reading every single solution. The first practice test I got a less than 15 - a 40% - (couldn't even get to the cube counting and pattern folding). Then after a week and a half/ two weeks, I still got a 17. However, now that I am practicing more and more, my average has gone up to 21/22. TFE and pattern folding were driving me insane and even after reading Ari's explanation and approach 2-3 times, I still had no idea how to do them. But after practice (almost two weeks) it really will "click" for you just like learning to ride a bike. Even angle ranking (the one that everyone says is impossible) can be learned with practice.
I still haven't taken my DAT (8/8 is my doomsday) so I can't tell how you how well my approach works.