My back has been hurting a lot lately because i sit in class from 9am-4. it hurts so bad that it's very hard to concentrate. what helps for the pain?

Ruptured disk?: You may have a ruptured disk. See your doctor. If so, physical therapy will help but time will be necessary. In the meantime, there are non-narcotic analgesics he/she can give you to tide you over.

Stretch & exercise: As you're finding out, sitting for long periods of time can be bad for your back (& health). Since you can't/shouldn't skip class, ask your professors if it's ok to sit in back of room so that you can periodically stand up & stretch w/o disturbing him/her & other students around you. Short of that, stretch btwn classes & exercise before or after classes. Otc nsaids can help but have side effects.

Back pain: For 23 yo there are many otc product like tylenol (acetaminophen) , aspirin, Motrin plus many analgesic lotion, cream, rub, balm. You may also apply tylenol (acetaminophen) patch or ice-hot cold patch before class. If the pain persists then see the doctor for ankylosing spondylitis, spondylolysis or congenital spine deformity. Please read otc pain killers http://doctorrajput.Com thanks.

NSAIDs and Support: Try nsaids such as Ibuprofen or even adding some tylenol (acetaminophen) for symptomatic relief. However your sitting posture might be off. Try getting a lumbar support or cushion to place in your chair while u are in class to help correct the imbalance. Relax the back store has many options to help with this. Also take a break every 1-2 hrs to stand or walk to take some stress off your back.

Exam/exercise: 25y fem w. inveterate back pain w. prolonged sitting in class + "fatigue" should have Osteopath's evaluation. Soft tissue spasm likely & program of aquatherapy + gentle yoga might help; plus soft homogeneously-supportive mattress to forestall pain-interrupted sleep & fatigue. Massage & topical Cannabis salve to be considered. Such symptoms in female warrant evaluation for Hypermobility Syndrome.