I'll know on the 27th for sure. I'll cheat and use home pregnancy tests earlier though, even if I know they're not totally reliable.
It's impossible to know without testing anyway with all the meds we get, plus women usually get signs at 6-8 weeks (it will count as 4 weeks if it's positive on the 27th).
Thanks for the good thoughts everyone... I remember stressing out for exam results, but this is way worse...