Why Am I Having So Long Menses After My 4th Implanon?

Hi i am on my 4th lot of implanon, the other 3 times its it has been perfect, and i never had my period but in January this year i had my new one put in for the 4th time and its totally different and i have had my period for almost 4 weeks now, is this normal? and will my period finally stop after this amount of time