dark spots on skin!

So, I know dark spots are normal on the skin during pregnancy but I had my hair up last night, and my husband saw this brown spot on my neck and said it was a perfect circle. I looked at it today and it's the same shade as all the other areas that have been darkening but I think it's weird that it's a perfect circle. Do ya'll think it's due to the pregnancy or something I should get checked out? 
Also realized how hairy I am when I took this pic 😑