low hcg levels and pain


hi ladies, my LMP was 24/12 and i got a very strong positive HPT on the 31/12 as well as severe lower abdominal pain (felt like pressure) which lasted a few hours, could hardly move. Since then ive only had some sharp pain here and there as well as back pain. Which i thought would be round ligament pain, but im not sure. I got a blood test done on the 1/2 and my HCG levels were 242 but according to the sheet they gave me it should be over 1k for being around 5-6 weeks?! I havent had any bleeding but the doctor said it could be an ectopic pregnancy? im freaking out a lot. i have an ultrasound tomorrow and currently waiting for another blood test, but i wont know the results until tuesday. Any advice would be appreciated! this is also my first pregnancy