D.W.
If you are ready to wean, need to take medication and he's not nursing right now then you've got all the signals you need that this is the time to do it while it will be less stressful for both of you.
I wean my daughter at 20 months and even though I knew I had done the best for her and it had been 20 months it's still hard/sad. It is letting go of one part of their babyhood and moving on. And it's hard to give up that control that this is something that is good for baby that only I have and giving it up to the cow or the soy or whatever. but we have to do it at some point and it sounds like this is your time.
It can take time for your milk to dry up. I started on bc after I weaned my daughter and my milk was gone in no time flat.