reacuring rash, unknown cause

I currently have a rash in my underarm, groin, between the fingers of my left hand, left wrist, and under my mouth. I believe it started at the underarm but  cant really be certain. Its been here for about 3 days and seems to be getting worse. It is red, bumpy, and swollen. It IS NOT poison oak,ivy, or sumac as i get that regularly and know the difference. This doesn't pus even when scratched, nor does it show a clear path of spreading. This has been a recurring thing in my life and ive had it probably half a dozen times since i was a young teenager to now at 23. Obviously i cant be certain but it seems to come from "inside-out" so to speak. that  is to say... i havent come in contact with anything unusual in all the times ive had it. At this point i just want some idea what it is so i can have insight as to how to treat/prevent it, if possible. Thank you.