Bleed

So I am suppose to be 6 weeks 2 days and the other day I had severe left pelvic cramping and no bleeding well that night I went to have sex and during it I started bleeding so I went to the er and they did a ultrasound and said I measured earlier then I'm suppose to be and my hcg levels are low. the bleeding wasn't heavy and it has stopped completely within an hour of being at the er. any stories from anyone who has gone through this would be appreciated. I can't call any doctors till tomorrow and I've been extremely worried....