Miscarriage?

Went to my first appointment last Thursday and they would only do an abdominal ultrasound and I measured at 5w1d even though I should’ve been 6w6d (very certain about ovulation date). My HcG was 33,000 on Thursday and I had it redrawn today and it’s only gone up to 48,315… I know it’s supposed to double every 48-72 hours and we aren’t quite doubled. What do you guys think? I’ve also been having some mild cramping and was spotting a little the other day.