My first question to you is do you get the shakes no matter what food you eat? 2) Or, the shakes specific to certain types of foods?
Here's what I would do if I were in your shoes; ask the doctor for a referral to an Endocrinologist (diabetes specialist). I also suggest you start monitoring and keeping a log of foods you consume. Log what you eat, how much you eat and how you feel directly after, 1 hour, 2 and 3 hours later. Do this for every meal, including snacks. Present this log to the endo. One thing I'd question the endo on is your pancreas, if it's producing too much insulin when stimulated by certain foods, thus causing a large drop in blood glucose levels.
Good luck and I hope he/she uncovers and resolves your shaking problem.
You might try googling Reactive Hypoglycemia and see if it sounds similar. I don't know much about it, but I believe it is a condition where people become hypoglycemic after eating (low blood sugar). Ask your doctor.