That's a really good idea about the positive messages, I need to remind myself it can and WILL be ok. I too check for bleeding throughout the day!
I'd say, if you dtd 4w 2days ago then you would be around 6w2d pregnant now... Possibly 1 or 2 days less.
With a textbook cycle, you would O on day 14 which means you are 2 weeks pregnant before you even conceive... So if you have long cycles, I think they just add 2 weeks to the date you ovulated/inseminated.... But dont quote me on that...
either way, you will find out how far along you are by the measurements from your dating scan. yay!