Suggest Treatment For Recurring Rashes On The Waist

I have a recurring half dollar size oblong rash on the back right side of my waist. It happens several times a year lasting about a week. It leaves a scar and is always in the exact same place, except this time it has moved over 1/4 and looks the same. It is raised and has bumps that looks like water blisters, itches constantly for a couple of days, then it is slightly painful for a couple of days, then it gets dry and rough. I can usually tell its about to break out because the day before it breaks out I have a deep pain in the top of my hip bone on the side. Seems that my lower back aches more during this time. Been having this problem for several years, but so sporadic and not too severe, never had it checked. this week is the second time in a row in 3 weeks. Its located just above the belt line.