What Causes Pain In My Buttocks?

hi for years ive sufferd with really bad stomach problems,but cant find anything,ive had colonoscopys segmanoscopy,and the one down my throat 5times,i had the segmanoscopy just over a year ago,but still everything came back normal,but since feb i been having this aching up my bum,and also feels quite moist all the time,it doesnt leak onto my boxer shorts but it feels quite squidgey up inside me