If you are having sciatic which is a sharp shooting pain down the back of your leg and into your foot then this is caused by nerve root compression
in the lumbar spine
. This can be diagnosed by and MRI
of the lumbar spine. It colds although you have a number of other medical problems at the moment and these could be contributing to this problem and so I suggest that you Dr assesses you urgently and organizes the MRI scan of your spine if they feel that this is the cause of your pain.