Is it normal for my areolas to change shape, size, and color within days?

Over the past few days my areolas seem to have gotten much smaller, lighter and feel softer then usual. Could this be normal or should I have reason for concern? I had a recent ultrasound on my breast which came back normal but there was still no clear reason as to why this is all of a sudden happening. Could it be because it is that time of fhe month? My primary care doctor ordered ultrasound just to give me a piece of mind after finding no sign of any abnormalities, but I still feel uneasy.