I Have Had A Rash On My Underarm For About

I have had a rash on my underarm for about a year now and it has spread to my right breast and now is on my right lower abdomin and now on my lower left abdomin. It is reddish in color light red it doesnt itch or burn and it is spreading all over .It does not have bumps or isn't raised. however I have noticed that i have develope terrible gas lately. My dr. hast treate with all kinds of creams and antibiotics with no results. Do you have any clues