[wanna be a young mother]

Ok I am lost as to what is going on. So you ladies are my last resort. This maybe a baby TMI question so be prepared!

Nevy has had diarrhea for 3 days now and when it started she got a small rash. It was just a red area and so I thought it was from all the wiping. Well its getting worse. I ALWAYS use a diaper rash cream at every changing no matter what. I have been doing this since birth. So what I dont understand is why this rash is getting worse??? It is only on her "private" area and not on her butt area. I dont know how to describe it without this being a little "weird" but its only on her outside area around the crack by her "private" area..... Ok I know that was TMI but I just wanted you to get an idea of what I mean. Could this still be a diaper rash or is it something else? She still has diarrhea and I try to change her diaper very often. I have not changed anything (meaning detergent, diaper/wipe brand ect.) I am at a lose for what this is or what to do about it. Any help would be wonderful!!!