Ttc after the pill

Its been about 9 months since I stopped taking the pill. Since stopping my average cycle has been about 40 days. Is this normal? Currently... my last AF was April 9 - 12 and was expected to start May 20. Normally AF is pretty heavy and short (about 4 days) but the last few days I've had extremely light (not had to use pad/tampon) brownish discharge. Possible implantation spotting? Its 3 weeks after glow shows my fertile window. Bfn on the 29th though. If not pregnant is it normal to "skip" periods? Will this screw up my next fertile window?