Do you use a full stop after a question mark?

No, you do not. A question mark or exclamation point replaces a full stop.

*

The answer above is correct.

An exclamation or question mark replaces the full stop and signals the end of the sentence!

*

I respectfully point out that is does matter...the question mark and the exclamation mark come first, followed by the full stop. For example, the following Words with punctuation are presented in this way..."What child is this?". Without the full stop you would be not aware that the sentence was concluded.