If you got stretch marks when did they appear, and which part of your belly was affected?

I'm 40 weeks 1 day and only last week I started noticing that the skin around my belly button looked shinier than usual. Now that I look at it closely it appears to be the beginnings of a ring of tiny strectch marks around my belly button. I'm not even 100% these are stretch marks but thats what they look and feel like to me. I always thought that if I got any stretch marks they would be on the underside of my belly but its totally smooth there.. I'm really hoping that these arent "real" stretch marks and that they fade away after birth