My baby won't stop pooping

So for the last 5 day a my baby has has really bad diorrhea and I've had him at the doctors becauae at one point there was blood with mucus...but he didn't seem at all concerned...this is day 5 and he's still pooping his little bum is red raw... and I dread changing his nappy because it hurts him and he screams....I'm at a loose end..he is teething but I don't see what difference that makes... seems to be feeding ok. No as good as usual but he is drinking some milk- won't touch his solids...any one else had this issue?