happen to me randomly once a year, went to see a doctor who told me it was only hemorids because id didnt eat enough fibers from cereals,vegetables, fruits. (I used to not eat fruits or vegetables for years...
Happened again to me 3 months ago, didnt eat a fruit or vegetable (hate em!)since months, only tuna, chicken and rice.... I got what I deserved! lol.So i started to eat vegetables and fruits again, and it disapeared in only two or three days.
But you should check it by a proctologue, you never know, maybe it's actually worse than just hemoroids.