I've Been Having Problems With My Bowels For About Six

I've been having problems with my bowels for about six months. I've had constant pressure and like I always have to push and go but most of the time just a mucus like substance comes out. My stomach was rarely feeling normal and I always felt sick. I went to see a gasteologist and had a colonostomy, he said the only thing I had was internal hemmoroids. That was about 5 months ago. Still i get bad stomach pains and get nauseas almost daily. I recently I've noticed with the mucus and stringy diarrhea like stool little sac like bubbles I thought it was only when I wiped but then I looked in the toilet and it was filled with them. What is going on? Is it something serious?