Pick pad app is very good you have to used it for at least 2 months might take awhile for your body to get Wright but it'll give you your best chance xx
I've never been on the implant but I came off the pill to get pregnant and I had to wait for my body to get back to a normal cycle :) it took about 5 months. So I'd say keep trying but don't stress yourself out about it, when your body is ready it will happen xx