pregnancy question sorry it's long!

So three weeks ago I took a pregnancy test and it was super light but was a positive. I called the doctors because of the complications I had with my daughter and they said that if I wouldn't change my mind about not terminating the pregnancy then there was no point in them doing a blood test on me and to retest in a week. So I retested and got a negative result. This past Thursday I went to the doctors because I have been feeling sick and low and behold I'm pregnant...but they keep telling me they don't know if the pregnancy is viable because my blood levels aren't doubling 😢😔 my first level was 82 on Thursday 125 on Saturday and 212 on Monday. I am super nervous and they think it could possibly be ectopic but I can't have an ultrasound until the levels would be over 1600 which isn't until next week! My husband and I were not trying and were actually preventing but we both really want this baby.