AM I PREGNANT ? ? ?

Oka so I finally went to my 6 week pp check up on March 20 , 2017 , and I took a urine pregnancy test and it came back negative . . . So today I have some spotting and I was wondering if this is my period starting or if it's implantation bleeding( because obviously me and my SO didn't wait 6 weeks , more like a week) but anywho I'm freaking out and should I go back and get blood work done instead ? ? ? 😬😬😬😬😬😬😬😬😬😬😬😬😬😬😬