Low back pain, mid back pain, frequent urination, bloating and pain in upper abdomen, feeling full without eating much, breast pain. what can this be?

Check for pregnancy : If you are still getting your periods, this may be premenstrual symptoms, but given your age and symptoms you describe you should get a pregnancy test. If you're not pregnant, consider checking for a urine infection. Back pain may be due to musculoskeletal strains too from lifting heavy items, trauma, sleep disturbances, etc..