I'm in need of help ladies...

So this was my first round of Fermara 2.5 days 3-7 I'm in cycle day 11... Negative opks so far . Alil back story bout me.... I have regular cycles bout 30days lately I've always ovulated on my own but I'm really questioning it now bcuz last month I honestly never got a positive opk n this has never happened to me. I have a soon to b 8 month old baby and getting pregnant with him took only two cycles with no meds at all. We've been trying again for a few months n my obgyn felt it's time to try meds due to my age of 42yrs old.... My question is on Fermara when did you guys start having sex?? What cycle day? I test twice a day so I don't miss my surge but I feel like I don't wanna miss my surge at all.