im kiad 36 years old first day of my menstrustion is June 21 2017 im using birth control pills i finished the whole pack last june 16 2017 the stop taking the another pack of pills. my boyfriend and i made sex june 16 to june 21 2017 and the last sex is june 26 2017 i missed my menstruation for the whole of july but i have an light spotting last july 06 2017 only on that day. and i take pregnancy test aug 14 2017 and the results is negative how can i know if i am pregnant or not? when will be the best tiime to take the pregnancy test?