Hcg levels rising but not doubling

Amanda🌈3/26/21👼🏻1/10/2020&4/24/2020

My period was supposed to be March 30...it never came so took a preg test after being a week late and it was positive. I had a D&C in Jan 2020...I got HCG level drawn on 4/8-:264 and on 4-10: 363 and 4/13: 763 and now today 4/15: 859...they say my numbers are not doubling and I am getting a little scared since I already had a MC and that time my numbers were not doubling as well. Are there any positive stories or insights?