is a construction made up of the て-from of a verb or adjective (で for な-Adjectives), and the negated form of the う-Verb なる, ‘to become’. This expression describes the word that is attached to it as being ‘extremely (A)’, or that one ‘can’t help but do (A)’.
In most cases, てならない
will be used when (A) is something that occurs naturally, such as feelings. Due to this, a more literal translation is close to ‘to not be able to move on from (A)’. In this way, it just indicates that (A) is so intense that the person affected by it cannot do anything about it.
I was up all night studying yesterday, so I’m extremely sleepy.
Summer in Aichi prefecture is extremely hot.
I can’t help but to feel worried because I haven’t heard from my daughter in 5 years.
Caution - In addition to being spontaneous and uncontrollable, (A) will almost always be something that is ongoing, rather than just being momentary.
I can’t help but be extremely mad at her because she lies to me all the time.
This manga is extremely boring.