im pregnant but i dont know how ...

Brit
So I've been trying to get pregnant and i haven't gotten my period since dec 7, 2016. And i took a blood test in the beginning of January 2017, which came out negative. I also took another pregnancy test two weeks ago and negative. And then i go to the doctor like couple of days ago and it said positive. Now i went to check it out with the doctor and positive as well. But remember i havent gotten my period since dec 7, 2016. So they told me im about 10 weeks pregnant and 2 days now. So they did an ultrasound and they said that theres no baby in there specially if im 10 weeks supposedly so they're saying its an ectopic pregnancy. Im going crazy and i really dont want to loose my baby. But i just don't understand how a month ago it said negative and that was blood and now it says i am im so confused and scared. I want to keep my baby someone please help me