You can
DEFINITELY do both! Just BD as planned on day 15 and then try to figure out when you ovulate (easier said than done!)...The best way I've heard that you know you've O'd is that there is usually a shift in CM and it gets stickier/creamier and less EWCM/stretchy. Once it's like that, go for the O+12 and do it as much as you like. I've heard some women do the cutoff, the O+12, O+16, O+20, etc.
I hope this helps. I'm in the same boat, TTC a girl in a few mos and trying to figure out when I O myself. Sending you lots and lots of

