In my variety of English, this is simply wrong. I would say:Do you mean:
I have an earache.
I have earache.
I have a backache.
I have backache.
I have a toothache.
I have toothache.
I think you're misreading @Hermione Golightly's comment. She can confirm, but I think she meant to say that she does use the article.I'm getting more and more confused. But in post #3 a native English speaker said we can not say "I have a backache." or "I have a toothache."
In the WR Dictionary it's given in both forms:Look at Longman dictionary's example:
ear‧ache /"ûëreûk $ "ûr-/ [singular, uncountable]
I've got terrible earache and a sore throat.
As you see in this example the author hasn't used "an" and he has mentioned that this word is uncountable.