Vasectomies can sometimes be reversed, but if your husband had one, then I would assume that it was because he did not want children.
Please don't pressure him into having kids if he doesn't really want to be a daddy. Parenting requires much more than being a nice person and loving your kid - that's just the beginning of it. It requires a lot of hard work, a high emotional investment, and a lot of self-sacrifice. Your husband may not want to pony up with all that. If he doesn't, it doesn't make him a bad person or a bad husband - it just means that he's not the type of person who makes a good parent.
If you push him into becoming a parent against his will, he will only resent the child and you for it, and, in the long run, it will not be good for any of you.