Hi
asubhampandaGlad to meet test takers like you who are persistent and dedicated
With 6 months at the rate of 6 hours a day, and a score of 690, its clear that your concepts are at place.
Now, the challenge is bigger !
Pushing the score from a Q47 to a Q50/51 and pushing your verbal score to a V40+ is the next new chapter.
It needs different set of skills!- That of "locating" an answer and NOT just solving for every question.
Analyse all incorrect attempts from the OG. Try the advanced guide now and always prioritize on quality over quantity.
1. I have exhausted almost all the official materials till now and this is making me think subconsciously that I can't get my target scoreAns:There are around 2000+ questions that are official. Have you analysed every question of Quants and uncovered the various strategies that can help solve the question smartly? For verbal, are you completely clear on why the incorrect answer choices do not fit the bill? If you have done all this and yet stuck at 690, then there is something fundamentally incorrect and needs fixing. Take help and talk to mentors. Understand the gap. If you have not done this, then complete your analysis exhaustively.
2. I am not sure weather I should stick to a particular study materials or re-do the OG questions. Anyways I have exhausted the official mocks so I am not sure how I can assess my performance improvementsAns:First part , I have already discussed. For the second part, chose the official mock where you have scored the lowest or the mock that you have taken earliest. After step 1 (described above), retake the official mock and eyeball atleast a 50 point increase. If you are doing better, you will find new questions. A minimum 50 point increase is a measure of your progress. You can read my response on this topic here too.
3.Preparing alone seems like the toughest thing. I am lacking motivation to resume and I tend to give up when I get a sub 600 score in the mocks (mg mat mocks are good but they lower morale sometimes)Ans:Then Don't

Take help. If GMAT is the priority, do your research and chose a brand that helps you on one on one mentoring. You need direction and your application gaps need a fix for both Quant and verbal. mg mat or any other test prep mocks, according to me are to be looked upon for practice.
Not for assessment.
Here is my response post on this bit. Read it when free.As far as "lower morale " is concerned, this test is a test of your strategic thinking and decision making. I don't sugarcoat things. So pls take my words positively.
You will face trouble, low scores and a rough journey as the climb is steep. Be determined and since you are a persistent test taker, add consistent discipline and keep going ahead.
Dust off any negative emotion and just keep your blinders on.
Analyse, detect and fix gaps, move on if you have an incorrect attempt.
Think critically, think on alternate methods, detect traps if you have a correct attempt.
Analyse exhaustively and with a set momentum. Talk to your mentor if you feel low at any time in the journey.
Adding our story of Riddhi who moved from 630 to 720 by analysing the gapsHope my words have given some clarity.
Let me know if you have any questions.
Wishing you the very best.
Devmitra Sen
GMAT Mentor