Been studying for a year...Frustrated

Hi. I started prepping/studying for GMAT last summer (took MGMAT online course). Took it last December and did horribly (440) mostly because I didn't take enough practice exams leading up to real thing. Since then, I took all of January off, and started from the ground up from Feb to April. Taken about 2 practice exams per month, scores range from mid 500's to 610. Unfortunately, just finished another practice exam (MGMAT) and got a 520 (28Q, 34V). I am devistated. Going to B-school is a goal for me for next fall, but looks like this exam is my barrier. I do tons of practice problems (I have OG11 and both verbal and quant guides, Kaplan GMAT, Cracking the GMAT, GMAT 800 books, so I have the materials!) I spend 2 hours 4 days a week doing OG problems (10 questions, 20 min--20 verbal and 20 quant per night), but maybe I should be doing more? Looks like my biggest weaknesses are number properties and algebra. What else can I do to improve my scores in these categories? Oh, Data sufficiency is killing me too!

I don't know what to do. I know I can do it and I know I am much weaker in quant than verbal. I read on someone's thread that you should take one practice exam per week leading up to the actual exam. Should I completely erase my hopes of taking the exam the beginning of October and push back b-school another year? I just want to hit the 650 mark!!! HELP!