@wonder91,
Congratulations on contacting your doctor. Thank you for doing that. Did you tell them why you were taking the diet pills and that you were not eating much of anything? Did you tell them about the weakness and lightheadedness you've been feeling?
How about replacing those diet pills with a good multi-vitamin pill?
If you feel you can't replace both of them, how about replacing just one of them with a vitamin pill? Do you have any vitamins?
Vitamins don't make you gain weight and will help keep your body healthy while you are in such a flux about what your healthy body weight should be.