Birth control

I was on the pill for 3 days last month then got off of it and now I am experiencing sore nipples for a week and back cramping and since yesterday I see blood when I wipe but none in my underwear the blood was light pink yesterday and now it's light brown today my period is suppose to come on Monday I'm freaking out  my boyfriend and I have been having sex but we use a condom and he pulls out I took 2 pregnancy test they both came back negative is it to early to test again is this side effects from getting off the birth control or is this implantation