sonogram question help!!

I had this last sonogram last week I was supposed to be 7 weeks and 4 days I measured 6 weeks and 4 days but my sonogram looks nothing like any other 6 weekers I have seen I'm confused could there be a twin hiding or am I really the weeks I thought I was and the baby is just small? Help!! It's heartbeat was 124bpm what do y'all think? It was a vaginal sonogram