still producing breastmilk

so I'm still producing breastmilk all be it not a lot but when I squeezed my boob just now a bit of milk came out I stopped breastfeeding baby at 3 days old as wasnt working for both of us but more for baby not latching properly and not getting enough milk but was expressing after this for a few weeks but stopped as supply dropped too much so was easier to give baby formula all round and I've since had implant put in and on sertraline so I would have thought after basically 3 months it would have dried up completely by now obviously I'm not going to try and reestablish my supply as I have tried before and didnt work and also now on sertraline i dont want to take that chance