Stubborn breastfeeding toddler

Ashley • 💙 8|22|16 💙 due in March 2019

My son is 17 months old and I still haven’t had my period return! He is still breastfeeding (very stubborn and hard to wean so far), but I want to start trying for a 2nd baby. My doctor said I won’t be fertile until I wean completely. Any tips on how to wean? My pediatrician suggested just saying no and wearing a sports bra, but I work full time and need my sleep. He mostly nurses at night since I’m away from him all day. I’d really love if he slept through the night, but so far that hasn’t happened.