thanks for your question.
Unfortunately, you have provided very little information to go on.
I would however, still attempt to give possibilities:
What you have described may have resulted from a number of issues ranging from hypotension
(low BP), hypoglycemia
(low blood glucose), syncope
("fainting"), anemia (low hemoglobin
If the problem was only with the hemoglobin and platelet, one may assume that the hemoglobin may have been low. A few fairly uncommon platelet disorders
may cause a "fainting" spell, but these cannot be so easily detected without specialized tests.
So, essentially, I would suggest that you visit your doctor again, and attempt to get the details of these hemoglobin and platelet problems that were discovered. It would then be easier to render relevant advice.