HELP !!! what is my deficiency?

ok so am just gonna give some symptoms: i am very under-weight for my age(16), my lips get cracked and peels alot, my hair comes out easily, i get sick easily, frequent headaches and nausea....just to name a few but it has to be a deficiency of sorts, i am not sexually active so its not a STI/ STD and i have been trying to gain weight for about 5 months now and it seems am getting skinnier...please help!!