Possible miscarriage

I went to the ER today and the told me that my beta hCG levels are kind of low for how far along I am. I'm 8 weeks and he said at 8wks it's supposed to be around 15k but mine are only 13270. I go back on Thursday to get them tested again. All day I have been bleeding but just now its brown and slight chunky. Just pray for me guys. Please