How to ask him for a vasectomy?

My boyfriend and I have been together for 6 years. I’m 27, he’s 29. We’ve talked marriage and have a lot of our future planned out.

He knows I don’t want kids because of so much that happened when I was growing up. He knows it’s very serious to me. He supports this and loves me.

However, my fears of getting pregnant are so intense, and my desire to avoid motherhood is SO no-budge it’s not even debatable, I want to ask him to get a vasectomy.

I’ve wanted this for years but been too afraid to ask. I mean, I’ve thrown the idea out there but when I’m nervous I laugh while I talk so he may have thought I wasn’t serious. I’m too afraid he’ll think it’s selfish of me to ask.

He’s a gentle and loving man, so I’m sure it would turn out fine. I’d just like advice on how to ask, how I should word it where I’m coming across serious but not demanding. I want the security of a vasectomy, but I don’t want to feel bad for asking him to undergo surgery for me the rest of my life. I carry guilt easily.

Thank you ladies

*EDIT*

I don’t think I made it clear, but me and my man are actually planning our future already, and we’ve already gone looking at wedding bands together with our families. He just wants to catch me by surprise with the proposal. We take things slow, and we’re very open about the wedding/the day we seal our deal! So our spending the rest of our lives together isn’t a question. Kind of made me sad that some of you may have perceived this as a premature thing. And he is on the same page as me with not having children. My love has told me that he understands and respects my pain over the subject very much, and that he would be fine either way. He’s the most compassionate man I’ve ever met, he truly wants me to be happy. So it’s not that it “won’t work out” or that he’ll “change his mind”. Some of you are sounding as though this isn’t secure and this sincerely makes me sad. I guess there is no way to prove anything through a screen, I was just wondering how to ask him that’s all. Thank you anyway.