Beta HCG rising not doubling.. Help!

Chelsea • Married my high school sweetheart and had our first baby on 8/13/15 👶🏼👑🎀
Okay so my HCG levels are rising but not doubling. 7w5d. My first results were 31,119 and today's were 37,829. I've read that once you reach 6,000 it can take 96 hours or more to double. Anyone had experiences with this?