Hi! I've spent ages trying to decide as well - I've read SO much info it's driving me crazy! I had been following Shettles for the last 12 months, but like you I have very irregular cycles and I kept missing my window completely due to timing the 3 day cut off. Eventually I ruined my cut-off and was 1 day before 'O' and got BFP, but sadly m/c at 6.5 weeks. So now I'm back to TTC again and wondering if I really should try 0+12, because it took me 12 months before and I'm getting ever closer to 40 so time is running out.
After my extensive reading (obsessed!) the most important bit (for me anyway) was the 'New zealand study' under the 'gender methods' on this site. I was shocked at how many boys were conceived using 3-5 day cut-off! Surely that disproves the Shettles theory about male sperm not living that long? I'm using a CBFM - which doesn't always show the 'high' days leading up to 'O', but always shows my 'peak' days - so doing 0+12 would be a lot easier to manage (although still not guaranteed to meet the correct timing for the egg)
My ds was also conceived around O with frequent bd, so I'm wondering whether to try the opposite and have DH abstain, and try 0+12.
Anyway sorry for all the waffle, its nice to feel I'm not alone in this. I think I am currently moving towards doing 0+12 but I'm now struggling with the decision over whether to do girl diet (will be a nightmare for me!), use replens, which vitamins etc. Oh why is this all so hard?!!
Good luck! Hope we both get lots of pink baby dust xx