TMI help

Okay so I am on the second year of my second implanon bar. My periods are usually quite regular, occasionally being irregular which doesn't bother me as it is a side affect. 
But, I've now had my period for almost 4 weeks!! That has never happened to me before the longest I've had it is about 9 days. 
But now this 4 weeks is really getting to me. I don't know what's going on. It's not heavy and it's more of brownish discharge. 
I don't know what's going on?!?!