it's more a matter of flow. you can use it that way and no one will think twice about it. you can use it as often as you can keep up!LOL! it is like saying "are you thinking what i think you are thinking?" you dont need to use it that many times but, it would usually work. it would be better to say," if you are unable to ask me -if or whether- your korean is correct." you can use "if" for each possibility in the sentence:)

Let me rephrase.... "If you are asking whether you are wondering whether your Korean is correct or not..." The second "if" means "whether". Actuallay you could have 3 ifs here: "If you are unable to ask me if you are wondering if your Korean is correct or not...." BTW.."thinking" in the sentence is incorrect!