I last had sex may 28th. I've had two heavy and regular periods for June and July. However, I'm 6days late for august. could I be pregnant?

Hello and welcome to EmpowHer,
You cannot be pregnant because you have had two regular periods since you had sex last.
It is a myth that women can have periods when pregnant. The vaginal bleeding that happens in spotting that last one or two days.
Having a late or missed period does not necessarily mean something is wrong. It is usually due to hormonal imbalances which is common and nothing to worry about.
Periods can be late of a number of reasons besides pregnancy. It is only a matter of concern if you are trying to become pregnant, or you have severe PMS without bleeding such as debilitating cramps.
Faith