Wanting another baby but can't. Help please.?

I have three wonderful, healthy children, and that was the mutual agreement between my husband and I. Once my youngest was three months, my husband had a vasectomy. My youngest is now eight months and I'm fighting with myself because I want a fourth child. I know all the reasons why I can't, but it's like a constant craving. I don't know how to stop it and feel like I'm going out of my mind. What do I do and would a hysterectomy help, even if it's just to tie off my tubes?