Help getting through 3 hours of Exam. Is it ADD?

Hello,
Took GMAT in feb this year. I received a 600 after 2 weeks prep. Went through Kaplan books very briefly , Princeton Review quite well. Did all the OG 11 questions untimed . 2 tests of Kaplan and 2 Gmat prep tests, neither of which I could finish in the time allotted.


The Real test was bad, I could not finish the quant section , just ticked last 3 answers randomly. I was soo exhausted half way through verbal, and knew I was well behind on time. Had about 11 minutes left and 18 questions remaining. Weakest section was RC ,(reading speed is pathetic), and so I just randomly was ticking answers. When I realized that the test score was going to be miserable, I almost gave up and just tried to answer as many as possible. Left almost 10 questions (randomly ticked answers to avoid being penalized)


Just about a month ago , decided that I should take the GMAT again, this time really study correctly. I enrolled myself in Manhattan GMAT 9 session course. I have practiced quite a few OG 12 questions, timing myself and forcing myself to pick an answer in the alloted time. I am doing very well in class, in fact I know the content cold. I can answer most of the questions they ask on their powerpoint presentations even 700+ level questions.


Now I have reached the point that I can do most questions under the alloted time with a high accuracy. However, I do not know why I am so fearful of taking practice tests.. I decided to take a GMAT PREP test 2 days ago, and I got a miserable 530.(funny cause its lower than my previous exam, and now I have studied the content much better) Again, I am convinced that its not as if the content is the problem, but I just get lost in the exam setting. 5 questions into verbal, and I lost motivation. Felt like I just wanted to stop the time.


I feel like I have ADD or something. After a point all words start looking same to me, and I find myself staring blankly at a RC passage, or a even CR / SC.. The same questions which I know if I would have done one by one while practicing, I would have nailed them. Why is it happening to me that I cant sit through an exam ? I ended up ticking random answers to probably 18 questions out 41 and I was so behind on time


What should I do? I am so ashamed of telling my instructor my score, because he would be confused too, I am probably one of his top students , (you guys must be laughing at this statement seeing my score) - but the truth is that. Instructor at MGMAT class often asks me to explain answer solutions to other students as well. Has this happened to anyone, and can some please help me.


Should I practice reading 1000 pages of fiction books to increase speed ? Should I read LSAT RC. Should I go take a prescription of Adderall (ADD medication) , I dont know. I had scheduled my exam for 23 september, but am definitely postponing it. I know I can definitely get a 700 atleast. How long should I study from now? I feel like im done with all the content, but have given only one practice test.
Please help.

Thanks