What Causes Spotting, Twinging Cramps And Sore Breasts After An Implant?

Ive had my implant in since may 27th i had my first period 2nd june and not had one since for the past two days ive experienced brown spotting.. i feel little twinge cramps and i have sore boobs.. i have had regular unprotected sex with my fiance but i have taken pregnancy tests which are neg so is this normal with the implant?