Missed period...

So me and my fiance aren't exactly trying for babies but if it happens it happens kinda thing.. don't want to put any stress on each other as we are getting married in May! :) I came off the implant early Jan and have been taking my pill (kind of) I was due my period a week ago. I've taken 2 pregnancy test both said negative? Could I be pregnant or just missed my period as not taking pill properly?? Help!