Typhoid fever and medication reaction.

I've been tested positive for widal test on 4 days ago with titration of 1:320for o type and 1:80for h type. I just had two symptoms at that time pain in knee joint and a bit of weakness. There was no pain in abdomen, no loss of appetite nothing like that. Doctor prescribed me pcm tds,doxim cv 200 mg. I started my medication 3 days ago and there was a lot of burping and heartburn but I thought it was maybe due to medicine so I stopped taking paracetamol cause i don't had fever and even now I have normal body temperature. But today i noticed the colour of my stool it was completely black though texture was normal so I again went to the doctor and he told me to stop the medication and prescribed me an anta acid syrup and esophag d tablets for the burping for 3 days and then to back again after 3days. I'm worried whether black colour of stool  was due to medication or is it possible that I might have intestinal perforation?I have a good appetite,no fever nothing just burping and leg pain.