:confused: I want to get pregnant if my lmp was aug.5th when would my most fertile day b?

How long is your cycle typically? Here is a great Ovulation calendar that will help you out:
Ovulation Calendar - Free to Use

I can not tell you your most fertile day. The best any one can do with out tracking physical changes (such as hormones in urine and cervical mucus) is to tell you your fertile window. The Ovulation calendar alkalineangel gave you will help you find out what that is. You are given a number of days and your body may ovulate at the beginning or very end of the window. However just having sex a few times in the window does not guaranty you had sex during ovulation. When using this method I would recommend having sex every other day during the window. This will keep your mans sperm count higher.