Took the plan b pill on my period...?

i had for the first time and im sure i was on my period, my bf pulled out for a second and noticed that the condom wasnt on . he said he pulled the condom out of me, im thinking it came off whn he pulled out, we stopped having right away, i took a shower and peed(sorry graphic) then we went to walgreens and got the plan b pill, i took it right away and then 12 hours later, the next day i have a white thick discharge, what should i do? could i be preg? does the pill work diff. if you are on your period? and what does ovulation mean?? pls help!!!