Some pregnancy tests say the can be used a couple days before missed period is this true and how accurate will it be last period 3rd august?

True, but wait...: Patience is a great virtue. One can wait until missing a regular period, or after 3 weeks have passed since having sex (if periods are irregular and one doesn't know when then next regular period will come). There is no need to test sooner, even though a positive test would be accurate (a negative test done too early may be a false negative result). One should be patient.

Pregnancy test: A home urine pregnancy test won't turn positive until 10-14 days after conception. Using the 1st urine of the morning will concentrate the beta-HCG hormone in the urine. So it should be accurate provided it's been longer than 14 days.