I agree with Jeremy that there are a lot of variables that go into a "how long should I study" estimate. There's no simple answer to that question.
First, you have done a FANTASTIC job so far, so congratulations on all of the progress you've made. I know you're frustrated, but you should give yourself credit for what you have accomplished; that makes it more likely that you can continue to accomplish more.
You mention that you cannot take a class or work with a tutor. Is that because of a scheduling problem or a financial problem? ManhattanGMAT has, in the past, offered classes occasionally for which students have received financial aid (that is, the course was heavily discounted). Another web site, Beat the GMAT, also periodically holds contests for which people who demonstrate need can get discounts and possibly even free courses from a variety of companies. In other words, if you're having a financial problem, there are still ways that you might be able to take a class.
I'm mentioning this because it sounds like you've hit a bit of a wall, and you may need some outside help to get yourself to the next level.
This is what worries me, and I cannot finish the quantitative section, usually 7 questions left.
What does this mean? Do you mean that you leave 7 blank at the end? You guess on 7 at the end and get most wrong? If either of those two things is happening, then the good news is: your quant knowledge is already at a higher level than your score shows. The bad news is that timing problems are preventing you from getting that score.
Take a look at the below article; it has a ton of links to other articles that will be helpful for you, I think.
http://www.beatthegmat.com/mba/2010/03/22/the-best-of-beat-the-gmat-mgmat-how-to-study-listGiven the timing problem you described, you may want to start with our free e-book, The GMAT Uncovered (the article describes how to get this book). It will help you to understand how the timing works and what implications that has for taking the test. (Alternatively, you can just believe me when I say: you cannot let yourself run out of time like that. You will always have to guess on some problems, so guess on the hardest ones as you see them during the test. Then, you won't be forced to guess on a bunch in a row at the end.)
Then go back to the beginning of the article and start from there. If you have any questions about any of the steps or activities described in the articles, come back here to ask!!