I'm in the same exact situation. Even down to ovulating on cd 20! My lmp was 7/10 (maybe 7/11), but I ovulated on 7/30. So the charts say my due date is 4/17, but the baby is a week behind. I am going to tell my midwife to put my dd at 4/24 for that reason.
With my last baby, I have about 5 different due dates! I had my homebirth midwife, who I delivered with, but early on thought I might go with a midwife practice for financial reasons, and they changed the date from my lmp after I had an early u/s, then I had my own from dates, etc. and the baby was born on that very day that I calculated! Not that its an exact science or anything, but it was validating to prove to everyone that didn't listen to me, that I did know what I was talking about!