Too soon?

J • Sat, Dec 27 • Mom to Baby Boy conceived through IVF- pregnant with #2!

I just got off bc a few months ago so my periods are regulating themselves. According to glow my af was due xmas, I tested this morning and bfn but af has not come yet either. If I change my af on glow to come on 1/2/14 which would be 28 days from my last af) it changes my fertile window by a lot! Hope there's still a chance