bleeding at 18 weeks

Last night I had bad cramping for a couple of hours and then started bleeding. It was a medium flow but very mucousy. I went to the er and once they saw the babies were fine with an ultrasound they sent me home with no other information other than to not have sex or use a tampon. I still have cramps and bleeding but it seems to be getting lighter and the cramps less frequent. I see my ob this afternoon and will hopefully get some answers about what is going on. Does anyone have any second trimester bleeding stories with good outcomes to get me through this wait before my appointment. I'm so nervous and I feel more lost than ever about what could be happening  after my ER visit.