Early ovulation?

My only plan pregnancy was with my twins in 2009 and we conceived them only a couple of days after my menstruation ended.

I've been trying to conceive with my fiance for 3 months, and we do have sex almost everyday except for during menstration and sometimes it's on and off the week following that. We always have sex every other day or everyday during my calculated ovulation period ovulation, but with our combined health I'm frustrated that we have not yet conceived. This will be our 4th month trying.

Is it reasonable to consider the possibility of early ovulation? That a woman, me in this case, could I ovulate on between days 6 and 10 of her cycle rather than later?