too soon for OPKs

so today i went to target and bought OPKs to start using them on sat, CD 11. however this is my first cycle off of BCP. should i wait a couple of months before using them to see what happens with my cylce, or just start using them now? the Q&As in the booklet say to wait 3 or more cycles before using OPKs, but i don't want to wait that long, i'm impatient

on a side note, why is everything so much $$? the cashier at target commented on how much $$ the OPKs were, and i got the target brand, then i went to CVS and got pre-conceive, and that was $18.99 the money we're saving my joining the cheapy gym is gonna go right to TTCing