I have a rash on my left buttock its four small clusters. At first I thought I had been bit by a spider. It's raw and itches I've had it for 4-5 days?

Herpes? Whenever a rash seems "clustered" you have to always worry about "herpes". Herpes infection may occur anywhere on the body. It almost always itches. See a dermatologist for diagnosis.
Im concerned that u. may have a small outbreak of Shingles,which can be a contagious disease.U need to have a physician examine this rash today and treat appropriately.