Thanks for the query to H.C.M. Forum.
You mentioned only few things as ,
I B S====diagnosis,
Weight loss==== 50 lbs,
mucus & blood in stool
May be due to Bowel fistula,
hormone producing tumor, lactase deficiency
H I V ( if contamination i.e. contact)
There are so many other reasons .
Upload all reports , there after any diagnosis could be made.