First things first. You are having symptoms which point out to different systems involvement at one time. For starters your stomach pain, green stools and on and off diarrhoea
point to a persistent infection in your colon
). I suggest you undergo stool testing and meet a gastroenterologist for a proper diagnosis. You might require to take antibiotics for some days. As for your back it is a congenital problem but now that it is giving you problem I suggest you meet a spine surgeon
. The most probable diagnosis according to your history would be spondylolysthesis due to a pars interarticularis
defect. You might require different xrays to check for the alignment and also probably an MRI to rule out nerve impingement. If that is found you might require a surgery to stabilise and decompress your spine .