Is It Possible To Get Pregnant While Being On Implanon?

I've had the Implanon birth control since december. The past two months i havent had a period but monday it came on really short and very brown. Before then my breast were heavy and you could see alot of veins. I've been extremly tired and eating alot and I have had unprotected sex more than once recently. But is it possible to get pregnant while on Implanon?