Undetectable glucose tolerance problem.

I have normal blood sugar levels fasting 94 and pp 113 Also fasting insulin 10.7 pp insulin 39.9 All post prandial tests are done after 2 hours. My problem is after eating meal after two hours or more than that I feel my glucose is low and I also feel slightly light headed so I take 1 or 2 glucose tablets and then I feel better.  I have shown to each and every doctor from head to toe but no one is able to detect my problem All doctors have recommended me multivitamins absolut 3g or supradyn, but after taking absolut 3 g I have breathing problems and supradyn I have low blood pressure problem after some days, so I discontinued. But I did not have the glucose issue after taking multivitamins Note During the test I didn't take any glucose tablets.