6 weeks 1 previous miscarriage and scared

My doctor believes I'm 6 weeks. I've have bad cramping on and off for a week. None for the past few days. But then brown spotting then nothing for a day and now slight pinkish scant amount after bowel movement. Had u/S on Wednesday yolk sac was sent no fetal pole or detectable heart beat. Hcg 7256 on Wednesday and today 14693. Do you think the scan was just to early?