Periodically I get what appears to be a bug bite at the apex of my gluteal cleft or above. It starts as an annoying itchy thing then gets larger as the days go on and fills with pus. Then it pops and the itching subsides as the days go on. I used to think it was stress or heat but I don't think so anymore. It happens several times a year. It can be one or a small cluster. Any ideas?