Trying for number 3

I need advice on how to get my husband to work on baby number three. We have two beautiful little boys 4&2. I’ve always felt in my heart like 3 would be perfect. But my husband won’t give me a straight answer. One day he wants one and the other he’s calling to get a vasectomy. (Cancelled two appointments, because he was “scared” but he called this morning to schedule another one) Please give me any advice!