Need some help

Before anyone jumps on me, I am plenty old and able to take on a child, but not necessarily TTC. My long term boyfriend and I live together and I am currently not on BC due to the implant screwing with my cycle. I had it removed in May of 2016 I have been keeping track of my periods, which have been very routine. 
While we usually use the withdrawal method, sometimes it doesn't end in the correct way. We're just leaving it to the man upstairs ❤️. We are pretty sexually active and I was supposed to get AF 3 days ago according to this app. Usually, I get AF the day before predicted. Well, the day I was supposed to get AF I had very slight cramps ( just enough to feel them, but not super painful like usual AF cramps) and literally ONE drop of light pick blood when I wiped. Ever since then, nothing. Fast forward 3 days, I took a pregnancy test this morning, and it was negative. Can anyone relate? If so, what was the outcome? 
Thanks in advance!