Talk to Gynecologist on Pregnancy

I am pregnant with my 2nd child and as per my LMP (3 Oct 2020) my baby's gestation age is 34 weeks and 5days but as per my ultrasound and per abdominal examination my gestation age is 36 weeks and 5 days. So what week should I consider for my delivery? Plus I am having severe inner thigh and back pain with pressure. All the blood tests and labs are under normal ranges.