Is the following sentence grammatically correct: I do do shopping on weekends.
The negative of this statement would have been - I don't do shopping on weekdays.
But a friend of mine said this is incorrect grammatically. Why?

Is the following sentence grammatically correct?

I do do shopping on weekends.

The negative of this statement would have been:

I don't do shopping on weekdays.

But a friend of mine said this is incorrect grammatically. Why?