Weird discharge, nearing end of Nexplanon

I'm in a little panic attack, and have been for the past couple weeks. So I've been on Nexplanon (Implant) for almost 3 years now. It expires in less 3 weeks. I had unprotected sex 2 weeks ago. Though he "pulled out" I am still having a lot of symptoms of pregnancy. I've been testing for the past two weeks and it's been a negative every time. However, I have had very light brown spotting and occasionally a stringy like brown discharge. My periods are irregular but they usually come around the end to beginning of the month. When I had unprotected sex, it was right around the time it should have started. Now I'm getting brown spotting and the weird discharge around two weeks after that. I'm wondering is there a chance I'm pregnant because of the expiration of the implant and I'm testing too soon? Or am I getting symptoms of pregnancy and weird discharge because of the ending of my birth control. Please, any thoughts would help.