If you're b/f you can have implanon.
It is similar to the mini pill but is a much lower dose due to being directly relesed into the bloodstream. Unfortunately it didn't agree with me and I had it taken out after 1 year but I'm sure it's not the case with everyone.
There is also the IUD if you want to go there, though probably not if you're looking at TTC in 18 months.