Is this a miscarriage again?

I am 6 weeks pregnant, and since about 4 1/2 weeks, I have been experiencing light spotting of brown color. In the past week, I have been on and off experiencing red blood, but just today at about 5pm I have been bleeding non stop. It's all red blood (like a period color blood) and I have been having nearly golf ball sized clots along with the bleeding, and have been soaking a pad every hour on the hour, if not earlier than that. I have been saving the clots so I can get them tested, but what I am wondering is if I should just go to the ER now, or if I should just wait it out until Tuesday, when the doctors office opens as it is 4th of July weekend. This is my 3rd pregnancy, I've had one live birth and a previous miscarriage 3 months ago. I'm thinking I should go to the ER to confirm miscarriage since I've been bleeding for 5 hours straight now, but I just want your guys stance on this before I do anything. Please help and thank you.