Measured 5 weeks

According to my LMp i would be 8 weeks (last week for ultrasound) i had levels checked and they were 27,000 which they said was in range with the measurement of 5W (not with gest LMP) i did a redo yesterday for levels check and only went up to 30,000. I have another ultrasound next wed and im just so scared... im still in range for what I should be measuring(6w now) but its so sad to not know whats hoing on inside. This is my second pregnancy, we have a 14mo son... im high risk due to history of seizures... its so hard to keep my mind off this pregnancy and find comfort