
Welcome! I think it's pretty normal to get + early. I don't usually test until I hit the two week mark, but I did with dd2 and got one at 10 days.
Well, I'm not following your dates. If you think you o'd around the 5th, then the 19th would have been 2 weeks later. You would be about 6 weeks today.
But don't worry about the u/s measuring you a bit behind that. It isn't an exact science. I mean, they put a dot at one end of a tiny blob, and then another at the other end, and then they hit "compute". The computer measures the distance, and spits out a number based on averages. If the tech put the mark just a little higher, you could be measuring ahead.
So, if you figured you o'd on the 5th, then your adjusted LMP would be December 23. Which makes you due September 27th or 28th, depending on how you count a completed week.