Are you finishing the sections? GMAC has made it clear that there are severe penalties for not finishing a section, this could be pulling you down a ton.
In regards to any other potential issues, I would definitely contact the course provider and try to work with your instructor. I would definitely suggest going through the fundamentals again as that will likely help the most at this level. From what I have read on this site, the
error log helps a lot more once you have mastered the fundamentals and need to focus only on a few key areas (thats my understanding at least).
Do the questions make sense when you revisit them later? If so, then it may be more of math errors than a lack of fundamental understanding.
There is no one study plan that works for everyone (depends on work schedule, motivation, etc...), but I would definitely look to refocus on the fundamentals for each section. This should help you establish a base level of knowledge. From there you can build upon it for the next two weeks (or longer if you push the exam back).
One last bit of advice that helped me out a lot. Remember that the GMAT is a reasoning test, not a math or grammar exam. Every question had incorrect answers for a reason and it is important to be able to understand and identify why an answer is incorrect. For almost every question there is a trap answer and a crap answer. It is absolutely not necessary to solve every problem for quant.
Best of luck with the rest of prep!