Stop breastfeeding

I need some advice. My son is 15 months old and I’ve been trying to stop breastfeeding since he turned 1. I need to take medications that don’t do well with breastfeeding but he’s not ready to let go. He’s also not eating anything but breast milk and I’m worried about his weight. I don’t want to breastfeed anymore but he cries and cries until I give in again. So I just stop cold turkey or is there anything else I can do?