Addicted to babies!

How do I convince myself I am done?
I have always wanted a large family. I adore babies.
My partner and I have 4 kids together. 2 at school, 2 under 2, the youngest is 4 months. We also have a dog, a business and a home to renovate. My house is a bomb site, I cannot keep on top of the washing and cleaning. I'm running on about 4.5hrs sleep a night. As much as I love my wonderful children, they drive me nuts, the older ones anyway. I feel like I am pretty much at maximum coping capacity.
I know so many people who have had miscarriages, Angel babies and complications. I know am blessed to have four pregnancies resulting in four healthy clever children without so much as an allergy between them.
Although I have had no major health issues, I am not good at pregnancy. I was so uncomfortable, with the last one particularly, that I could barely walk in the end and my body has sustained a major baby beating!
I feel like to go again would to be really pushing my luck.
The thought of doing it exhausts me.
We are ok financially. Not great but ok. We can afford everything we need and the kids don't miss out. But I am concerned about coping long term.
We decided we are finished, it looks like a vasectomy is on the cards, yet I still have the feeling I'm not done.
I am trying to dispose of as much baby clothes and equipment I can while we still have a baby as I thought letting it go would be easier, its not, its agony.
I get asked almost daily if we will have more and I find I am saying no with less and less resolve.
I have friends with 1, 2 and 3 children who's stomach turns at the thought of another baby . Why can't I feel like that?
Physically, financially, logically we are done. My head says no more but my ovaries scream yes!
How do I get over wanting more babies?