I knew immediately but it was confirmed when skipped af at 4/5 weeks. Called the docs straight away and was told didn't really need to come in unless I wanted to - I did! Needed the reassurance, so went in the next day.
I was around 3-4 weeks each time. Here we don't get a doctors appointment, my GP doesn't even confirm it if you've gotten a positive home test because he says their test is just the same thing.
All I did was phone the GP, tell the receptionist so it could be logged on my file, and then get the number for the community midwife. Rang the MW who invited me to a group meeting that same week where they give generic info on tests, what to eat/avoid, etc. and blank copies of hospital notes. Then a 1-2-1 appointment at 10 weeks with the MW to complete hospital notes, do bloods, etc. and she booked the scan for 12 weeks.
I found out when I was 4+4 and went to the doctor after I had cramping for an early scan at 5 weeks. Next scan was at 7 weeks, as 5 weeks was too early to see anything, apart from it not being in my tubes