Wrong due date

Elizabeth
Hey guys... So I was to believe I was 7.5 weeks along however had to go to the ER last night due to cramps and some spotting. After the ultrasound they informed me I only appear 5.5 weeks.... Which means one of two things. 1)my date was wrong or 2)the pregnancy stopped progressing. I can't find out until further tests... So for 7-10days I'm going to be going crazy... Just wondering if anyone else had been told a due date then after ultrasound found out it was totally different?