Blood from back passage, abdominal pain

On and off for around 2 years I have suffered with abdominal pain sometimes severe when I have been taken to A&E numerous scans blood tests etc, nothing found other than small amount of fluid on my pelvis, the scans concentrated on my ovaries fallopian tubes etc. The pain eventually eased. A couple of weeks ago I began experiencing a large amount of blood when passing stool. To the point I couldn't see my stool due to the amount of bright red blood I wasn't straining either so ruled out anal fissure. This happened numerous times along with mild to moderate abdominal pain. GP did rectal exam and ruled out piles, requested blood tests which was clear. I have been required to do a FIT sample. The bleeding has now stopped. But still suffering with abdominal pain and change in bowel habits. Has anyone got any advice? I'm thinking the worst, did anyone else experience this?