“can’t help doing something” is an interesting English expression. The form is:
can’t help + gerund (spoken form)
cannot help + gerund (more formal written form)
Here is an example of its use:
This means that I can’t stop liking Sarah. It is not intentional, but I like her. Something is making me like her. I know that I should not like her (because she shouts at me), but I still continue to like her. I can’t help it.
So “can’t help doing something” means that we are not able to control something.
Here are some more examples:
Mark: “I’m sorry but I can’t help it!”
When Mark says “I can’t help it!”, he means that it is not intentional, but he just can’t stop losing his keys. He can’t control the fact that he always loses his keys.
Here is another very common example of when to use “can’t help doing something”. In this example, Mark is on the bus and he hears a private conversation behind him that he would like to reply to:
“I couldn’t help overhearing” is a very polite way of telling somebody that you heard their private conversation, but it wasn’t intentional. In this example, we say “couldn’t” because it is the past tense. We couldn’t control the fact that we heard the conversation.
Here is a question for you all. – Elvis Presley sang a famous song with “Can’t help ______ _____ ______ (3 words)” in the title. What was the full title of the song?!