If your doctor is a genral practitioner it might be a good idea to go to a dermatologist. A lot of times if it's something specific/esoteric a general doctor won't necesarily recognize it or know what to do with it. I have Alopecia and until I saw a specialist I didn't really get any sort of serious response or treatment.
Vitamins can't hurt (and can certainly help your overall wellbeing), but if your hair loss is extensive it's not going to be what stops it or brings it back. I also don't have a great deal of faith in shampoos etc. that promise to stop hair loss. I would really recommend finding a good specialist if you can. Sometimes you just need to keep sticking your foot in the door until you get the response you need.
Best of luck with finding a solution..unfortunately stress does not usually have a short term "magic bullet" solution. Seeking out alternative solutions such as acupuncture (which can be implemented alongside onventional treatment) or even something much more basic such as exercising can be great for dealing with a stressed out body.
Is your hair loss all-over or in patches? Is your hair generally brittle? Does it break easily? Do the hairs that fall out have a small white ball at the ends? How long has it gone on? I ask because that might help narrow down what kind of hair loss it is.