I have hypoglycemia, and the way they found out was by doing the 6 hours
glucose tolerance test. It is not fun, but very accurate. I would ask your doctor about having it done, it takes all day, but, you are in the lab and if anything should go wrong, you will be taken care of. Also, since they got that low of a reading, they should have drawn it again, that just does not sound right to me. I would see a good endocrinologist, they specialize in problems like this.