Cramps/ spotting :(

Having some cramps and brownish/pinkish spotting today, wasn't supposed to have my first ultrasound until 12 weeks but went in today at supposedly 9 weeks to check on things. Nurse could only find yolk sac and no fetal pole or heartbeat. They drew blood to check my hcg levels but won't know those until tomorrow and I'm supposed to go back Monday for more blood work. The nurse seemed to think I am just much earlier then I was thinking because my periods have always been somewhat irregular but that seems like a huge difference to me and I'm super worried! :(