I Am An 18 Year Old Female That Has Been

I am an 18 year old female that has been dealing with lightheadedness for a while. I have went to 2 different doctors. One suggested that I increase my salt intake the other put me on florinef because he thought something is wrong with my adrenal glands. Being on the medicine has helped a little bit I still get lightheaded a lot, especially when I drink coffee. Sometimes it gets to the point where I start vomiting. I was wondering if anyone had any ideas of what's wrong?