When Is my Actual due date??

I didn't know I was pregnant. I have a PCOS so I wasn't really worried why my Menstruation hasn't come up. So I went to an ObGyne and had an ultrasound so I saw the baby I was happy. He's kicking a lot. The doctor said that I am 18weeks and 1 day on September 1, 2020 and that my due date is on February 1, 2021 is the calculation of my due date right???? I counted the weeks but it shows that I will be having my baby on the last week of February or first week of March#firstbaby #1stimemom #advicepls #pregnancy #theasianparentph