How to know how far along I am???

I go to the doctor tomorrow to confirm my pregnancy but I don’t know how far along I would be. Is there a way they can tell how far along I am? if I haven’t had a period come back since I stopped breastfeeding my first born. It has been about 1.5months since I breastfed my first for the last time. I have been nausea for about a month (starting when my little one and husband had the stomach bug so I didn’t think much of it) and I took home pregnancy tests getting positive results on 7/13/19.