My very disappointing preparation status

Hello all, I'm stingray and I'm knid of new here.

I have started preparing for GMAT around 2 months ago. I have been reading posts here for quite some time now and recently joined here and started posting. After reading lots of posts this is how I began. I bought Princeton Review, Kaplan, OG 11 and Kaplan 800(not studied this yet). After completely studying the PR and Kaplan I took the GMAT Prep1. Then I have completed all the problems from OG 11. I have also gone through the Wiki Study material on this web site. I have completely studied the Manhattan SC Guide (downloaded from their web site). I bought the GMAT Club challenges and finished 8 of the math challenges. I have a full time job and have been spending an average of 20 hrs a week preparing.

Here is how I have performed so far and it is very disappointing.

1 month ago: GMAT Prep1: 590 (Math-17 incorrect/36 & Verbal - 18 incorrect/41)

2 weeks ago: OG 11 - Incorrect: PS - 35%, DS - 35%, CR - 19%, RC - 25%, SC - 28%

This week and last week: GMAT Club Challanges:

Test Correct Total % Correct Percentile
m01 19 37 51.3% 14.8%
m02 25 37 67.6% 33.0%
m03 20 36 55.6% 26.9%
m04 22 35 62.9% 38.2%
m05 20 36 55.6% 26.3%
m06 17 34 50.0% 27.6%
m07 21 34 61.8% 38.1%
m08 13 37 35.1% 9.1%
I'm keeping a log of all the problems that I get wrong and also the ones that are difficult for me. I review them and plan to re-review them.

After reading so many posts with advice and confidence builders this is the best I could do so far. May be I just don't have it in me. I'm not really sure though. I took GRE in year 2000 and got 2070/2400 (Math - 710, Analytical - 750, Verbal - 610).

What am I doing wrong? CEOs, Managers, Interns, anyone please comment. Thanks and I really appreciate your time.