Actually, water retention can make a noticeable difference.
I know I retain water; I've seen myself on days when I don't. Muscle definition is much more prominent, and I'm constantly running to the bathroom. On days when I am retaining water, my socks leave lines on my legs, my feet and fingers are puffy, and muscle definition fades. It happens quite frequently, and it's a difficult thing to conquer, but it's not all in my head.
Also, I doubt it has much to do with being female either, since in my case, water retention is very sporatic.
So it could very well be that you are retaining water. A clean diet can help, but if you are already eating clean, like I am, then it's a mysterious condition.