I have to pee often but when I take a pregnancy test it comes back as negative and I am on the implanon?

Lots of stuff. There are a variety of things that can cause one to urinate frequently including a urinary tract infection, drinking lots of water, type ii diabetes, and many others. If you are having any burning with urination, that makes UTI more likely. If you are eating a lot and losing weight, that suggests diabetes. This is definitely something to get checked out with your doc.
Possible UTI. Some pharmacies have UTI test strips, otherwise suggest you see your dr. Or nurse practitioner because you may well have a uti.