I second the doctor visit- same thing happened to me, thoguht it was a hemmorhoid, turned out to be an abscess. Horribly painful, finally burst
open, now I have a fistula that will not go away. It sucks. Even if you are absolutely, positively %100 sure it's a hemmorhoid- go see the doctor anyway. At least they'll be able to treat it properly, if it is that, & give you something better than Prep. H. And if it's an abscess, they can drain that too & save you a lot of pain & potential problems down the road.