How soon can a pregnancy be confirmed by a transvaginal scan???

I’m currently 5weeks and 1 day and 19dpo.

My home test lines are getting darker and darker.

I went to the ladies clinic just a hour or so ago and my doctor looked at the progression of my home tests and said I am definitely pregnant, he then did a internal scan (they don’t confirm by blood tests where I live) but said he couldn’t see anything yet.

So yeah my question is how many weeks do you need to be in order from the pregnancy to be detectable on via internal scan?