Talk to your doctor. It could be what intertrigo like Janey said. Also there are some women that simply don't put out enough hormone to get a positive pregnancy test. I have two friends (sisters) that neither one of them got a positive test until they were 5 months pregnant.
I am late for my period i didnt get it at all last month and im waiting for it this month, the thing is that my breast have been really sore and itching. I took a pregnancy test at the end of november but was negative. Why is this be happening to me?
If your test was pregnant, then it's more likely to be a case of intertrigo ( the same thing has happened to me ) and it can be easily treated by your doctor.