Yes, it is very possible. The older your baby is when your fertility returns, the more likely you are to O before ppaf. You can start charting to keep track of things.....temp., cm, etc. Before you actually O or get af, though, you will most likely have patches of ewcm that don't lead to O.....or spotting that doesn't lead to af.
I bought a ton of internet cheapie opks and kept track of it that way, too. I would have thought I O'd a bunch of times if not for my negative opk's and temps. I think I paid $20 bucks for a hundred pack of opk's.
I started charting before my DD turned a year b/c I was getting signs.......5 months and 284 negative opk's later, I just got a positive! But if you want to catch the first egg, and your personality is such.....(I'm a poas addict) daily opk's will do it for you!
Good luck!
Dee