Hubby has "reservations"...

Jamie
We've been married 3 yrs and his vasectomy was about 7 years ago. Between the two of us we have 3 kids, 15, 11, and 11. I've always wanted another and was very clear before marriage. In November, we decided we'd get VR with tax return and he was so excited! And now he just keeps coming up with excuses not to have the surgery. I know he doesn't like change. How can I convince him that change isn't always bad and that we should follow through on the promise he made me?