So my boyfriend and I were curious and he decided to go inside me with just one stroke without a condom. It was just one in and out. He did not finish but I was still scared about pre-cum so around 16 hours later I took Plan B. Around 10 days after I bled for 7 days (very lightly), and I thought "what if its implantation bleeding". I tracked that as a period and on my Flo tracker it says I am now 28 days late and I'm not sure when I'll get my period. I've also taken 6 pregnancy tests with all of them at least 2 weeks apart. All negative. Please help