thank you for sharing your complain, if you have pain on back/flank with abdominal pain which radiate to pelvis/bladder and sometime it may be associated with burning or difficulty in urination, you should keep in mind possibility of ureteric/kidney stone. tenderness and pain on right illiac fossa also indicates of appendicitis. so you should first comfirm diagnosis by blood & urine investigation and also sonography of abdomen and pelvis. after final diagnosis take medicine rather than taking medicines randomly. low back pain may be due to muscular pain.for temporary relief you can take analgesics like ibuprofen or muscle relaxant like aceclofenac+paracetamol+chlorzoxazon, with omeprazole/rabeprazole.it will relieve back pain and abdominal pain. hope this answer will be helpful to you. for more queries plz don t hassitate to ask. get well soon dear friend