Trying not to get too excited or freak out too much, but spotting and cramping on CD15 has NEVER happened...

Okay, so we'll all agree this has been the weirdest cycle ever. (Well, I will say that, and you can just take my word for it, okay?)
I am normally very predictable. When not on bcp's, AF generally comes between days 22-27, with no spotting or cramping between periods. So on CD 15 (today), why did I just start spotting a little and having moderate-turning-to-give-me-meds-type cramping?
Is it from stopping bcp's? - this is my second cycle since stopping. Is it this implantation spotting/cramping I've heard about but never experienced, even though we supposedly have 0 sperm to work with? Is this related to the left lower quadrant pain from the last few days? What is going on with my body?
Is it okay to take naprox*en for the cramping? Should I test, and if so, when? Not sure if I should be happy or worried...