I have only just seen this...
Also a March BFP here, and I think we just got lucky! 2nd month off the pill after 4 years on it, we did have lots of sex and I looked out for the EWCM, then BD'd even more, that was it really!
Where I might have more advise is, never test before AF is due, always try to wait until she is at least a little bit late, I tested the day before AF was due, BFN, tested again over the next couple of days, BFN, waited for a whole week convinced I wasn't pregnant and that AF was just taking it's time after only being off the pill for a while, finally nine days after my AF was due, I got my BFP, and that was only because my DH practically forced me to take the test!!
Now I am 26 weeks gone, due 25th November, with another little boy
Good luck to all who are trying, I do remember how frustrating it is. TC xxx