It actually just looks to me like your cycles are regulating. They NEEDED to shorten, because you were having really long cycles. You've been charting for four cycles, and now you are really starting to recognize the patterns of your cycle, and it doesn't seem to me like four cycles of not getting pg is quite x-ray time yet. (I'm not counting the cycles before since you weren't O'ing.) That said, since you actually had a pretty great looking chart this time around, it's possible you might want to try some other strategies. I know it sounds a little counter-intuitive, but maybe even BD less? Although I know TCOYF says most men produce enough sperm to be fertile every 12 hours or so, I feel like from anecdotal experience with friends and this board, some women seem to get pg when they back off from that really aggressive BD schedule and give DH enough time to recover in between. This happened to me too--with DD, I did not get pregnant after having perfect charts for several months and BDing many times during the fertile window, but then one month we only BD'd once during my fertile time, and that was the month I was pregnant. Same thing happened to other friends. Might be worth a shot before you get tests on you. Good luck!