Implantation?? So confused.

Al
I'm really getting nervous. I had sex two weeks ago a day before ovulation. We used a condom but I'm afraid of any rips or tears. He didn't ejaculate but I've heard plenty of stories about precum. So I took plan b 36 hours later (I'm over the BMI limit). Now my period is supposed to come in two days. However, I've had some cramping and brown discharge in the past week for a few days straight, along with headaches, bloating, slight constipation, and sore boobs. Today the discharge and slight cramping continues. I thought it was my period coming almost a week early since plan b can have that effect. But nothing and it doesn't feel like it's coming anymore. I took a First Response HPT even though it's early and it came out negative. Can someone put my mind at ease? Does this sound like implantation bleeding and symptoms? I know I have to wait probably another week to test but my anxiety is driving me up a wall.