Ok so I had sex with my bf about 3weeks ago, a week after sex I had light bleeding, I thought it was my period but it didn't get heavy like I usually am on the first 2 days, it lasted 4 days, I toke a pregnancy test 4 days before my period it's negative, then I waited 2 days before my period negative, then am 4 days late now about 2 be 5 days late nd on day 6 am be exactly 3 weeks that's if Iam, I toke a pregnancy test today it came out negative do u think I can still be pregnant, 1 more thing I use the withdrawal method