Dear all,
Before I talk more about my GMAT problems, I'll like to share few details about my academics so that you can help me easily. The last time I did mathematics was in my high school (was kind of good back then) and after that I never had math in my academic life. I'm into commerce/business stream and for subjects such as accountancy and costing, I use calculators. I scored 4.0 GPA in both undergrad and masters(one semester left though).
I'd been preparing for GMAT since quite a few months (on an average 5-6 months). I know it's too long! I wanted to apply for Fall 2019. I started with quant basics (referred high school mathematics books) as I'm pretty weak at math. I solved a test paper on GMATPREP1 and scored 260 (Aug'18) !! I was shattered. Well, I calmed myself thinking I've time to prepare and that this was just a beginning. I purchased OG and did quite well. I also went through the solns for better understanding, for both quant and verbal. I did not use any timer. Feeling pretty confident, I solved the GMATPREP1 again and scored around 360 (aug or sept, maybe). Well, I couldn't study full time as I'd college and research/academic projects to be done.
I again went through various concepts of both quant and verbal from gmatclub and solved relevant questions. I studied like 5-6 hours, on an average, daily. I solved Manhattan Advanced Quant Book (twice in a span of two months), and did OG again. I also went through SC rules and CR tricks. I gave various free tests such as GMATPREP(1&2), Manhattan, Veritas etc and kept scoring between 500-580. However, 580 that I scored on gmatprep was a bit elevated as I was familiar with few questions.
Here is the analysis that I did. Initially, I'd been scoring less because my quant was weak and wasn't familiar with verbal rules. Even after studying so much, I was still scoring low because I was able to correctly attempt only 50% of the questions. My verbal score improved to 35-38 but quant is still behind. Most important thing that I noticed was when I solve questions without any timer, I'm able to solve well (not excellent). With timer, I mess up so badly, because of anxiety or whatever reasons, I end up making silly mistakes. Also, at times, I forget to use tricks and shortcuts in questions, especially with timer as I'm in hurry to complete the question/test before the time runs out.. For verbal, I'm not excelling in assumption questions which hampers my performance on CR and RC questions. I have done hundreds and hundreds of questions still no improvement!
This entire thing is really stressful. Being a bright student in academics (always first or second in class), it's really embarrassing to be a failure in GMAT

! Thinking about this entire failure thing gives me nightmare and stress of-course. It really pisses me off

!!!! I wanted to apply for Fall 2019 but because of my performance, I'd to postpone the entire plan to Fall 2020. Like everyone, I too wish to score 750+. Well, coming back to reality, I honestly want to score between 650-710 which is a reasonable good score. I want to give the GMAT exam before March 31st, 2019, as I have other academic commitments, and want to apply to tier 2 universities of USA (I'm bit discouraged to apply to top universities after thinking and predicting my gmat performance

). I can't delay the GMAT prep more. My family insists me to join some classes but I don't think that'll give me any value addition as they teach a bunch of people and really don't care even after charging you a huge amount! I have friends who had been to such classes and had no much improvement. Moreover, I also went through LOADS of successful GMAT stories, on how to prepare, approach the questions etc, to get help but couldn't adapt to it as everyone has different methods of studying or maybe I wasn't able to apply it in my case. I'm literally tired of everything now. I really need some advice on what should I do now? Where should I begin? I must mention and also assure you that I'm thorough with the concepts. I can study 5-6 hours daily. I really really need some help and honest advice because I anyhow want to finish off this gmat successfully asap.

Thank-you.
Regards,
Depressed and brokenhearted.