Help Please, I Bled Today!

Hello everyone, this will be my 1st baby ever! So my 1st pregnancy! I am 7 weeks according to my OB.

I got home today from work a few minutes ago and went to the restroom. To my surprise there was blood and now I'm scared. I had NO pain or cramps whatsoever! The blood was already dry, about a silver dollar sized spot and when I wiped it was brownish. I did have sex last night, BUT it was gentle and slow. Any reasons/advice/suggestions? I will call my OB tomorrow as well to ask questions.