I think I'm having a miscarriage

Yesterday (Saturday afternoon) I got back from the park with the dog and started to feel some cramping. Went to the bathroom and saw the dark, dark red blood. I screamed for J and started bawling. He told me to get up so he could see because I couldn't look. I did end up looking and it looked like little pools of dark red blood. Not a lot but enough to know something was up. 

We called the doctor's office and had the on-call doctor call me back. He said at 5 weeks, they wouldn't see much on an ultrasound but to watch out for pain on one side (tubal pregnancy) or very heavy bleeding/clots. If either of these happen, to call them back. I have to go in on Monday since I am Rh- and J is O+, so I'll have to get the shot if this is a miscarriage. 

Today (Sunday), I still have cramps (and back pain) and blood when I use the bathroom, enough to make the toilet water red. I'm not filling up a pad and the blood is not bright red, more dark red. I prayed last night more than I ever have before and I kept telling the baby I was sorry, I hope you are not feeling any pain. Is it wrong for me to be assuming the worst before even going to the doctor? I think I am just preparing myself. I'd rather go in and be surprised that it's ok than go in and be blindsided. 

I guess I should be happy we got pregnant on our first month trying, so clearly we can get pregnant, this is just God's way of saying something isn't right. I'm mad at myself for telling J's parents and two friends. I always said we were going to wait till 12 weeks, but the excitement took over and I couldn't help myself. I just didn't want to have to un-tell.