Suggest Treatment For Chronic Constipation, Stomach Pain And Bloating

Hi I have had bad constipation now for over a week prior to the constipation I had a bowl movement that was dark black I have had burning in my lower back as well as discomfort around the abdominal area. First I thought it was a kidney stone. The pain on my left lower side of my back seems to be getting worse. My stomach is very bloated. I ve tJen greens as well as Bio-k but nothing is helping me have a proper bowl movement what can I do? And what can it be?