What Causes Itchy And Painful Rashes On Anus?

I have just recently had a very itchy rash on my anus which has now formed several rather painful spots. It tends to be extremely painful to stand up suddenly and turn over in bed as i believe the spots may be rubbing against each other. I have tried putting antiseptic cream on the itchy rash, and it has gone down slighty. But i am worried it could be something else, because of these spots.