What contraceptive can i use to start menstruating again, after using depo-provera (3 years) and currently the nexplanon implant (since june 2016)?

Non hormonal: You need to consider barrier methods of contraception such as condoms, local vaginal products, and diaphragms. The use of a hormonal contraceptive will artificially induce a "period" but it is not a "natural" body produced period. If you use a barrier method, combine them (condoms + vaginal contraceptive or diaphragm + contraceptive gel/ cream) for more efficacy.

Combination pill: Nexplanon will keep you from having regular periods. The first step would be to get the Nexplanon out. Your periods may go back to normal after this. If not, you can use a combination Estragen/progesterone pill to give you regular periods. Progesterone only birth-control pills, Depo Provera, and the progesterone IUD won't regulate your periods. Best wishes!

Oral combined E+P: If you want to “start menstruating again” you may simply consider taking oral contraceptives pils which contain a combination of estrogens and progestins in a cyclic fashion .