How far along am I ?

I saw a doctor yesterday for my first visit after getting a positive pregnancy test. He just told me to get a blood test & ring today to find out approximately how far along I am then book in for my dating scan at around 6 weeks but my doctor had gone home & no one else really knew. My level was 100, the date of the first day of my last period was 18th June. One app is telling me I am 3weeks+4 the other is telling me I am 4 weeks + 1 . Does anyone have any idea ? Thank you in advance ❤️❤️