Well I don't think starting too early is going to hurt! But it really depends on the length of your period, length of cycle and length of luteal phase. For instance...My period is between 5-7 days. Then I have a couple days of dry/sort of wet cervical mucus, followed by maybe 3-5 days of eggwhite like mucus (the fertile time) and ovulate on day 15 (at least these last two cycles) and then dry up mucus wise and have 12 days of a luteal phase before af returns again. I personally start BDing within a couple days of my period ending as that would be about day 9 for me and you know that the 3-5 days before and day after ovulation really count. Then since we tested my DH's sperm count with home test I know that he has high levels with every other day or every day, so we try for every other day, but then when my OPK turns positive we really start trying harder! This month my OPK was positive starting on day 12 all the way through day 15 and started to lessen at day 16. I ovulated at day 15. Anyhow, I hope that helps. Probably the more of the month you cover the better...especially if you don't know when you are ovulating. If you don't check any of your fertility signs, you might want to start! Good luck!
My Doc told me to start BD'ing from about day 7 through day 20 of my cycle. He said every other day would do it. Funny thing is, we don't have time for that much you-know-what, but we are on vacation now and are gonna try. We will probably be in the nursing home when this month is over! My cycle is 28-30 days long....not sure if this will help you! Best wishes!!!!