hcg level question

Michelle
So on Friday I did my first beta test and it came back a 16 went again Monday and they came back a 66. Went back today Wednesday and the only increased a little to an 86. Has anyone else had this happen. I go back Friday and hope they are even higher. Dr did say since they didn't double there is a chance of miscarriage. I'm so scared. Been waiting for the bfp for 4 years and now have it and may lose it.