The Depo and Implanon are both hormonal. From your post I understand that you dont want a hormonal contraception? You can get IUDs that have no hormonal aspect and can be left in for years.

I you do get the Depo and it doesnt work for you you are stuck with it for 3 months, the implanon can be removed at any time.

From what you are saying I think an IUD that is hormone free would be the best option. Good luck hun.