Hi jOBRI3 -
Thanks for writing to us and seeking information. Vitamin D deficiencies are fairly common, and it's good that your doctor has been able to diagnose and recognize your situation. There should be no harm in your drinking a gallon of milk every week, but just to be sure you can ask your doctor about this the next time you go in. I would also provide information on exactly which Vitamin D supplements you're taking as well.
Here's an article that has a lot of helpful information on Vitamin D deficiencies, which tend to increase in the winter months.
People with dark skin, infants and almost anyone living north of about 40 degrees latitude – which is a significant portion of the U.S. population and most of Europe– are often severely deficient after months of inadequate winter sunshine.
Will you keep us posted on your progress, and whether you are able to increase your levels of Vitamin D? As you'll see in the article, Vitamin D is critical to good health in many ways.
Take good care,