Definitely mention it to your doctor when you go in for your appt. Until then, maximize your caloric intake when you can eat. Invest in some sort of nutritional supplement drink like Ensure or Boost, which are loaded with vitamins and protein. Eat small frequent meals, perhaps avoid foods with strong aromas and go for a blander diet like bread, mashed potatoes, fruits, veggies, etc. While I have been lucky this time around with the m/s passing after the first trimester, sometimes strong smelling foods will quash my appetite quickly and make me quite nauseated.
Andi
Also try to get your prenatal down with a few bites of something for extra nutrition.