Freaking out here.

I'm somewhere between 6 and 7 weeks based on my apps. And now the light intermittent cramping has been joined by spotting these last 2 days. It was light and brown before, so I was choosing not to worry. Now its red and getting heavier. I don't know what to do. If it is a miscarriage, there's nothing a doctor can do to stop it right? So do I just wait and try to get in to see my Dr tomorrow morning? We did have sex a few hours ago but nothing rough. So am I overreacting?