I agree with the answers above but I would like to add something.
Another situation you would use "I do have" (sub- to be - verb); when you are writing/speaking compund sentences.
I do have a gym membership, but I never go.
She does have a car, even though she never drives it.
Bob does like cats, unfortunately he is allergic to them.
They do eat ice cream, but only during the summer.
I am originally from California but living and teaching in Peru. Que tal!