A bit worried

So my pregnancy levels aren't doing so well. I'm 6 weeks and 6 days and two days ago my levels were at 32,000 and now they are at 35,000 Yes they are going up but they were supposed to go up by 15,000 but they only went up by 2,000. My dr said she is unsure if my pregnancy is viable. Has anyone else had this problem and still had the baby. I'm so scared I'm gonna lose this baby. Any advice?