I've been on the Nexplanon birth control for about 13 months now and have had very regular cycle until now. Instead of a normal flow I've only been spotting for the past 6 days. I've also been cramping pretty bad, had frequent head aches, changes in appetite, mood swings, and my breast have been swollen and tender. I've taken 2 pregnancy test and they were negative. Is it possible i could be pregnant?