How old are you op?
Did the age gap bother you when first started dating, or did you think it was cool for an older guy to be interested in you, and if there were other people gossiping and giving attention to your relationship, did you like the attention??
Were there no discussions about you wanting a family prior to marriage??
I am sorry that you are going through this.
It sounds like you are embarrassed by your relationship, him, or both and just really want to fit in with those around you and be accepted.
Also, perhaps there is guilt, regret insecurities, and shame within your self.
It doesn't sound like a happy marriage. Now you're feeling the need to lie about things and your partner whom you've spent 20 years with.
Perhaps you've always been miserable and bothered by things ..masking it..but now you realize the depth of your misery.
Chances are he is settled and content in his life, and wants no children.
If you want children and a close in age relationship, you're going to have to leave him..and find someone else.
Perhaps this relationship has run its course, and isn't meant to last the remainder of your life.
It isn't too late to have the family you desire, unless you are planning on remaining with your husband.
If you are truly unhappy, you should consider leaving..let your husband find someone he is compatible with who isn't ashamed of him and the relationship.
The both of you may be more suited for different partners now at this stage of
life.
Don't remain unhappy.
If you remain, don't lie about your relationship and spouse anymore. I would also make sure that he never comes across this post.
If you stay, don't let the desire of a family become to the point where you're set on making him a father. It won't go well for you.