Scared - possible chemical/miscarriage

Hi ladies. As many of you saw, I had a great surprise of a BFP last week, confirmed with a digital. AF was due last Friday. I had some pressure for a few days which I understand is normal and it has now today turned into constant dull cramping and dark brownish-red bleeding. I'm so scared I'm losing my tiny baby! I have my GP appointment tomorrow morning but I'm afraid it's going to be a long night. ????