heavy bleeding, changing tampons every hour

It's been two days and I'm experiencing extremely heavy bleeding. It's not normal for me. I'm changing my tampon every hour and it's soaked. I'm also using overnight pads and they get soaked every hour. There's a lot of clotting. I'm also having bad cramps. We've been TTC baby number 2, so my first thought was miscarriage. I read about menorrhagia and it says to see a doctor. My question to y'all- "can/should i go to the ER, or try to get an appointment with my obgyn?"