Implantation bleeding on nexplenon

So me and my bf had unprotected sex on dec 15. He didnt get to cum inside me but im freaking out about pre cum due to the fact that on the 26 of this month i started spotting light pink its now this morning it stopped completely and all through out the week it was supper light. Im aware that nexplenon could mess with the body and can have pregnancy symptoms but has this happened to anyone else? Should i be worried??