Should I stop breastfeeding?

Honestly, 18 months is already such a good run and you should feel proud of that, not guilty. If pumping after a full day of work and parenting is making you feel this exhausted and lost, that's your body telling you something important, and it's okay to listen. Your mental health and energy matter just as much as breastfeeding does, and your kids need a mum who feels okay, not one who's running on empty. A lot of mums I know have stopped around this point and their kids are absolutely fine, they just moved to formula or cow's milk depending on age. Maybe have a chat with your PD about the best way to wind down if you do decide to stop, but honestly, you've given your daughter a brilliant head start already.