How far along am I?

Just found out today that I'm finally pregnant after a year and a half! Here's the thing though, I have no idea how far I am! I took a digital that said 1-2 weeks (which I guess would be 3-4 weeks the way a doctor measures it), but I took it midday. I tried to use a due date calculator but they all need the date of your LMP. The date of my last period was may 17-21 and then I had 3 days of spotting June 24-27. June would be 3 weeks but I'm afraid since I took it in the evening, the hcg isn't strong enough to actually register the correct weeks.

Anyone have any idea how to figure this out before I go to my doctor in like, 5 weeks?