Confused

Ali

I was seeing a fertility specialist and I got pregnant during a rest month so they're not sure when I ovulated. Based on the date of my last period, it says I'm 8 weeks but after the ultrasound they said I was more like 4 or 5 weeks but my HCG levels are really high for 4 or 5 weeks (16,220 as of Tuesday) so I'm confused. Has this happened to anyone else where your doc isnt able to give a firm estimate of how far along you are?