hCG and possible multiples?!

I had my first beta done on 12 dpo that came back at 211. My second beta was done 7 days later at 19 dpo and was 4,011. I've read that they like your numbers to increase 60% every 2 days. By my calculations mine are increasing 132% every 2 days. I've been scheduled to have a sonogram in 6 days and am freaking out a little. The nurse said they want to "date" the pregnancy...but i know they're looking for multiples. I don't have multiples on my family, im under 35 years old, wasn't taking any fertility meds. Curious to hear from other mamas who had high doubling times and only 1 baby.