Are you, well, how do I put this, retarded?
OT: You should've taken a prep class, they're extremely beneficial. I'd suggest looking over old concepts you've probably lost over the years in math. I personally have no struggle with reading/comprehension or grammar, so I felt that wasn't much for me. The most important thing, aside from just knowledge, is proper test taking strategies for the ACT. You'll find there are a lot of them, and this will really give you a boost on the test. The most helpful tip I'd received for the ACT is to ALWAYS answer EVERY question. The questions in the math area will always progress in difficulty, they're not randomly arranged. Once you begin to struggle, know you don't HAVE to work out each question, that'll just take away from the time you could spend being sure your answers you know are correct. When you reach these, depending on the score you're aiming for, you'll choose ALL of the same letter. Answers are always evenly dispersed to each letter. In other words, you're guaranteed 2-3 correct answers. This is also helpful if you're low on time and just need to finish up quick, always be sure to do this.
Feel free to send me a PM if you'd like any more tips or advice.