Dear friend,first of all thank you for your consultation.it seems that you are really suffering from acute gastroenteritis.i sincerely believe trichazole is not going to do any harm your body.u can definitely take this medicine.as far as your back pain is concerned ,from my day to day clinical experience ,I am saying there are many causes of back pain.most commonly people get affected by muscle spasm in the lower back region.for that you should go for a regular home regimen of physiotherapy like vertebral flexion exercise.also take note of not bending forwards ,avoid lifting heavy weight or burden.if the pain becomes unbearable you can take pain medication like Stilpane.thank you.