Taking a Plan B twice?

okay, so i've had sex once before and it was not planned, so the next morning i took a plan b and i'm not pregnant and my cycle continued normally after that. this happened in the middle of october of last year (2016) and it's now january (2017). my boyfriend wants to have sex this weekend and we're both ready, but i'm still scared of the pregnancy factor. i've talked to my mom about birth control and she made me an appointment at the gyno for the beginning of next month. yes, of course i can wait to have sex until i'm on the pill but i just have a question- even if i used protection while having sex, and take a plan b after this weekend if we decide to have sex, is it still going to work since i have already taken it once before? is it going to be less effective and not work? i know you're not suppose to abuse the plan b and just take it whenever you want but this would be a one time thing until i get on the actually pill. is this ok?