At this point, I really don't think "looking better" is what is important. Rather, it's being HEALTHY. Frankly, right now I don't think your body has enough fat/nourishment. I would go to a doctor and ask about your BMI, what is a healthy weight for you, ect. Muscle weighs more -- so rather than worrying about the number on the scale worry about how you look in the mirror. ie. Hit the gym gain some muscle and definition and (your weight will increase) but you'll LOOK better!
Being healthy > Being skinny. Your health should come first.
(Please do NOT take this the wrong way -- simply worried/concerned for your well-being!)