Why am i getting this pain in my stomache. 10 points?

Im a 17 year old girl. Im 108lbs and 5'4. I get sick very often. My stomach hurts for no reason sometimes. But today ive been laying in my bed and it wont stop hurting. Its so painful. Its this burning kind of feeling. Im not allergic to anything and its almost like i need to throw up. My dad thinks im lying so i cant ask him. What is it? I happens almost everyday but never for this long usually its for a sec then stops