Fate and Fault

My last hope of being pregnant before August 25th, Snowdrop's due date, is gone.  12DPO and I have had 2 consecutive drops of BBT signalling AF is on the way.  I expect she'll arrive tomorrow starting off Cycle 12/Month 13.  I'm not upset I just feel kind of numb.  I really thought that this cycle would be it.  For the past 5 days or so I've had backache, cramping, tender breasts,  fatigue and most weirdly a strange metallic taste in my mouth.  Also I had this kind of thought that maybe fate would play a hand as if I had fallen pregnant this cycle I would have had the exact same due date that I had with my daughter.  I guess fate doesn't really exist.

Since Rosie was born just over 4 years ago I have not used any hormonal contraceptives.  I had the copper coil for a year but it made AF worse for me so I had it removed.  For the 1.5 years prior to TTC we practiced withdrawal (though I can't say we were very strict about it at all - fertile times/non-fertile times, we didn't pay any attention).  During that time 2 of my closest friends fell pregnant whilst only using the withdrawal method.  Yet here I am after 2.5 years of no contraception, 12 months of actively trying - using OPK's, charting BBT, logging every symptom and change - and still no pregnancy.  I have lost almost 40 lbs and am between 7-10 lbs lighter then when I conceived Rosie and still nothing.  I can't help but feel like I am to blame, what have I done?  What is keeping me from getting pregnant when everyone around me has managed without problem?  Am I being punished for something?  I don't know where to go from here or what the next step is.