I have been menstruating for a year straight. everyday. i have no appetite, and now i have low left back pain. it's not my kidneys. what could this be?

Could be many things: It could be multiple things. Start by seeing your family physician who may end up referring you to an ob/gyn physician. A proper exam is needed to be able to tell you a diagnosis.

Need endocrine work : You need an endocrine work up if your pap is negative, also you may need a d+c as part of the evaluation. You definitely need to see a gyn as soon as possible. Bleeding for a year indicates a real issue to be thoroughly examined.