What Causes Discharge Of Yellow Mucus During Bowels?

About 3 weeks ago I went to the toilet for a wee and passed a yellow jelly like substance from my bottom, ever since then, when I open my bowels there is lots of yellow mucus and when I wipe there is lots of yellow mucus on the tissue, when I have been to the toilet I have the feeling I still need to go for a while afterwards. I don't have pain but my period is due so currently have occasional dull period pain and low back ache. When I open my bowels I have small stools. I am not constipated and it's not diarrhoea. What is it?