How do I tell him o want to stop pumping?

I know OH will be disappointed but he doesn't seem to get how much it hurts. I'm going on 4 months of exclusively pumping and it's to the point where my nipples feel like they are being tore off every time. I just want to cry at each session. finding the time in the day to pump for a half hour every 3 hours isn't possible when I am solely taking care of our baby from 6am till 10 Pm.

How do I tell him in a way he'll understand?

We have a stock of over 30 tubs of formula but he wants more.