Ectopic pregnancy is present either in both tubes or attached to bowel. it mostly is caused when egg is unable to implant it self in uterus.
First things doctor do when they doubt ectopic pregnancy do a scan. if they are unable to find any sac even not in tubes they perform blood test to see whether HCG are there or no. Once the quantity of HCG are shown then they determine that pregnancy is in out side the uterus.
Spontaneous abortion (SAB), or miscarriage, is the term used for a pregnancy that ends on it's own, within the first 20 weeks of gestation.
HCG might have been done to see if they are dropping or increasing. if they were able to see a sac then they probably trying to figure out that you might be too early because dates can be wrong. doing another HCG will confirm that you have had a miscarriage already or you are going to have it soon enough.
Are you bleeding at the moment? if you are or you are having cramps best thing is to go to ER. they will be able to help you at once.
I am sorry to hear about this. Yes, if it is a tubal your numbers will not double every 48 hours. They should also see fluid in one of your tubes. There can sometimes be a sac in the uterus and fluid in the tubes. If you start having severe pain on one side please go to the doctor or ER. If it is a tubal pregnancy then you could have ruptured your tube and be in serious danger.
So sorry about all your losses. I think that if it's tubal then your numbers will rise very slowly....not double like they should. Seems like they would have seen something in the tubes tho, but not sure since none of my m/c's have been tubal. Again , really sorry.