I've been on Nexplanon for 6 months. I've always had regular periods. I started taking St. John's wort for a few weeks(2 pills 3 times daily) not knowing it could interact. It's been 3 weeks since I've had sex with my husband(he's been gone) but this past week I've been emotional, my breasts have been heavy and sore, I'm having skin changes, and light cramping. A week after we had sex I bled a little for a little under 2 days and it stopped. I was confused but didn't think much of it. Pregnancy tests come back negative. Can they tell so early? If the bleeding was implantation bleeding that would put me at only 2 weeks but I'm so confused by all the pregnancy calculations I just don't know.