<s>[INST] Why might my back hurt while I use the restroom(bowel movement) and when I try to sleep on my stomach?  Began after sitting for about 3 hours at a functionI am 34.  I weight about 167 5'4".  I fell about 4 years back and had very low back pain.  I told my dr that it felt like my butt hurt in the inside.  The pain I have now is not that low.  This pain has been going for about 1 1/2 now. [/INST] Hi,It seems that due to fall there might be having some spinal injury causing some pressure on spines and nerves due to sitting particular position or sitting for longer time.Go for x-ray lumbo-sacral region.Do back extension exercise daily.Avoid lifting heavy weight.Ok and take care. </s>