possible miscarriage

about a month ago I got a bfp 6 months past the birth of my DD. lmp was Feb 15. I had an ultrasound Monday and the fetus was measuring 6w1 day with a low heart rate in the 80s. ob said there's a 50% chance I'm miscarrying and wanted me to come back for a recheck a week later. well Thursday I started spotting and continued into Friday. just light salmon pink. I called ob and they got me in yesterday to check. there had been no growth from Monday and couldn't find hb. radiologist isn't wanting to call it final but ob is positive this pregnancy is no longer viable. they want me back in for a3rd scan Monday to confirm. no blood testing has happened since I got my bfp so I'm gonna suggest that Monday. I started having mild period bleeding today with the typical clots id usually get and some dull cramping so I felt doomed and figured this is it but I'm still keeping the radiologists glimmer of hope in mind but hard to when I never had this with first 2 kids. looping back around cuz my screen won't scroll back up. he thinks if this is viable that o'd really late but idk. I just want to know what is making the radiologust have hope and why the ob is so sure it's a mc. I'm tempted to call the on call number in the am and see if I can get in even tho I'm not soaking pads or having severe cramping just to give me peace of mind and not wait till Monday. anyone else been there with both positive and negative outcome in this situation?