Like you, when I was dating my husband, we agreed on two children if the first could be conceived quickly (he has a child from a previous marriage and was pushing 40). It took nearly a year to get pregnant, so we were perfectly fine with one.
When the time came for him to get a vasectomy, I hesitated. Not because I wanted more children, but because I didn't want to give up control.
With my husband's doctor, he required BOTH signatures from a married couple before the procedure could be done. It took me about 1.5 years to be ready to sign that paper, but my husband never pressured me on it. Like I said, it wasn't about having more children. I knew what I had agreed to when I married him (just like you did), it was more about giving up that control.
BTW, from a financial perspective, it's GREAT! It's just a specialty co-pay, which in our case was $35. WAY cheaper than any other form of BC. and it's GREAT not to have to worry about getting, paying, or remembering my own form of BC.