What Should I Do About Black Stool, Lack Of Appetite, And Persistent Abdominal Pain When Diagnosed With GI Issues And SIBO?

I am a 60 years old man , have been suffering from GI problem since long and started flare up since last year. Initially it was loose stool and lower abdo pain. Colonoscopy was done . It was normal. Doctor gave few medicines but there was not much improvement. Later the problem was bowel movement with constipation and occasional loose stool. I started lactifiber for bowel movement. Though it helps bowel movement but still cramps bloating etc persists. I had also upper endoscopy five years back. There was erosive gastritis. Now there is lower abdo pain and pain is not confined to specific area. Sometime whole lower abdo sometime left or right side lower abdo. Problem in bowel movement. Recently breath test was done which was positive for SIBO . Doctor prescribed cefomil -O , Rifagut 400 Evion and cyclopam on SOS. I took one cyclopam 2 days back. Now there is episode of black stool today , no appetite. As my GI problem is long since college days it was told as IBS. I am taking lybotrip DS since last 15 years once daily. Recently my wife has expired due to corona in 2021 may. Since then the problem is aggravated. Pl help.