wow i have no idea, but soda water!? never heard that before Lol.....if it were me i know i would be dying to test, but i reckon wait a little bit longer. doesn't the pill give you 'fake' pregnancy symptoms when you first go back on it? cause ive been on mine 2 weeks, and some days i freak out cause i know ive been really slack with it.... i guess if AF doesn't arrive by May then maybe test again? all the best