hi, i had unprotected sex due to condom break , i did get my period ,5 days late tho, it lasted 4 days, however i am on the pil but my cycle is 7 days .. after about 3 days i had heavy dark brown discharge for 17days, i did experience very dizzy spells , nausea aswell as lower backpain and headaches .. i took a pregnancy test which came back negative, cud i still be pregnant?