I dont get it? Should i go to m doctors or wait and see what happens?!

I dont get it? Should i go to m doctors or wait and see what happens?

I keep losing weight for no reason. I haven't changed the way i eat like having an apple instead of a candy bar. I am not over weight or underweight I am 13 4'10 72 and dropping
I am getting pains in my stomach and my lower back like a stingy feeling. All of my clothes keep getting bigger and I am getting bonier. Why am i losing weight for no reason? I am not even trying to lose weight.

ANY sudden or prolonged weight loss for no understandable reason does need investigation by your doctor. It could be the sign of an underlying problem that could get worse untreated. Diabetes is one thing that springs to mind, and celiac disease, is another. But only a doctor could help you find out what it is. Please see one as soon as you can, and if you can, write down anything that you have noticed that has changed (like your weight, those pains you mentioned), and for how long.