I'm 6 weeks pregnant and have been bleeding the last 6 days with cramping each day. I've done 3 u/s…

I'm 6 weeks pregnant and have been bleeding the last 6 days with cramping each day. I've done 3 u/s but no baby can be seen. my hcg level Wednesday was 1214 then Friday 2968 then Saturday 2720...so it went down a little. doctors are suspecting a threatened miscarriage, a miscarriage or ectopic. I go back tomorrow to get hcg levels and u/s done again. I'm on an emotional roller coaster!!! what is going on...why can't they see if there is a baby in my uterus or tubes at this point.