Ultrasound

Hello, I have recently found out that I am pregnant. I immediately informed my most recent partner and we had decided to look at abortion options. I was informed by my doctor I wasn’t able to make my first ultrasound apt. until at least 9 weeks and so I made an appointment at an abortion clinic. I wanted to know first before making that decision how far along I was so I booked an ultrasound appointment through a private ultrasound company and they informed me that I was 6 weeks and 5 days which would mean that my most recent partner is not the father ( my most recent partner had been 4 weeks prior on that exact date of my ultrasound). I had a regular period before this time so either my ultrasound was innacurate or I am indeed further along then I thought. I want to know forsure which one of those is most likely to have happened and what steps I should take from here as my first official doctors ultrasound isn’t scheduled for another few weeks.