Another "my only regret is not stopping sooner" poster here. Seriously, OP, it is FINE to stop. Or to stop pumping so much and supplement with formula, if that's what you want. I know it's really hard to believe that right now, but it's really fine.
When I burst into tears in the pediatrician's office the third time in a couple of months, her advice was "You don't need a reason to stop. If you want one: your mental health matters." I didn't fully hear it at the time because I was completely obsessed with upping my crappy supply, but looking back that seems so fundamentally true and too easily overlooked.