Please answer?? when should i test?

ok my lmp was on aug 18 and i bd on 29, 30 and sept 3. when would be the earliest that i could get accurate results with a hpt. I have had tender , and mild cramping which i never have since i had my first 2 children also sorry if tmi seems like i have alot more discharge then normal. I also figured i should be due for my af by the 16 of sept.