Twins? Pic inside

I had Dr. Appointment on Thursday 1/7/16 My Dr did an ultrasound said I was 4-5weeks he order me to get blood drown to see my HCG count that very same day and to come back today 1/11/16(results are pending). Should I be a little concern/exited? Because this morning the person who gave me my readings said I was being place at around 7 weeks because the reading was at 13378 the only thing throwing me off is Dr ultrasound said no more then 4-5, has this happen to anyone and ended up with more then one baby? One is a blessing two would be by far the greatest thing on earth!
What do y'all think?