It sounds like this is definitely a change for you and not your regular state of health. Anytime you experience new symptoms, including pain such as you describe, it is always a good idea to let your doctor
know. He or she may want to see you for a clinic visit to discuss your symptoms in more detail and also see if there are any suggestions of a diagnosis on physical exam (or perhaps the need for more testing).
Pain on the left side of the abdomen that radiates to the back could be caused by many different things, some of which are benign and others of which could need medical attention. In a woman, any sort of pathology involving the ovary can cause discomfort like this, including ovarian cysts or abscesses. If you are sexually active it will be important to make sure you don't have a condition called pelvic inflammatory disease or an ectopic pregnancy. Kidney stones
or urinary tract infections involving the kidney can also cause this kind of pain. It will be helpful to know if you have been having fevers or chills or any kind of changes in your urinary habits. Overall, the best thing for you to do in this setting is talk with your doctor or pediatrician
to help decide on next steps.