I have recently had the very same problem. I also recently changed my pill from the combined pill to cerazette. Ever since I have not had what I would call a "normal period" I have been getting slight cramps and brown discharge but no blood. I have also missed a day or so. I have been worried I may be preganant or have an sti or something, but im not sure. I have an appointment at the family planning clinic this afternoon. I will let you know the outcome as it may help you too.