Possibly pregnant? Need help

Miyana
I have been having aching breast and tender nipples for 2.5 weeks. When I brush my teeth I gag and get a sharp pain in my nipples. also a pain that goes from my boob to my underarm every now & again. That's the only symptoms I've had I've always been a heavy sleeper so I haven't counted that. I am on nexplanon it's my 4th year total so I thought it was impossible. My partner & I have sex almost every day without a condom....Can anyone give any suggestions or testimonies on how they found out?