11 weeks or

hello beautiful ladies..my lmp was aug 3rd..im currently 11 weeks..i went to my 1st obgyn apt he did heartbeat which was 175 [i google and they said between 160 to 170]..took him awhile to find heartbeat ...he said am i sure im 11 weeks i look bigger [i guess i got a big belly dr] but i do keep track of my period but could it be true could i be more than 11 weeks which would be weird or maybe twins? i go next week for ultrasound and its freaking me out