Help me figure this one out..

I have very long and irregular cycles due to PCOS.

My last period started on July 12th. I got a positive opk on the 15th August. Ovulated probably on the 16th.

Got my BFP 9 dpo on the 25th August.

Doctor is saying I'm 6-7weeks, I told her my cycles are long and I know I ovulated late, but she said they still go by LMP.

She told me to get a scan next week at 8 weeks, but I'm putting it off until I am actually 8 weeks (which won't be for either 3 weeks)

I'm assuming I am around 4+6, so didn't freak out when my HCG came back low for "6-7weeks"

Am I right to be going by my actual ovulation date?