M.S.
This happened to my daughter but we switched from pampers to the walgreens brand. We thought it was the diapers. Then when we switched back to pampers...the bumps still would not go away. We realized she was allergic to her bath soap and it wasn't the diapers at all! good luck!
FYI- i was just reading that the sam's club store brand diapers are made by pampers but are much cheaper. No clue if it is true, but we may try it to cut costs.