Off BC and Sex

Bree • I`m 27 yrs old and have one son (8). I just had our second. Not sure if we're done or not.
I went off my pills on Oct. 18th when decided we wanted to start trying. (Fiest time in 7 yts) I haven't had the first period yet. Wanted to know if I had to wait to start trying( until after a few) or if we could start sooner? Anyone know why they say to wait?