This might be an effortless question but I really can't understand a grammatical aspect of it.
____ I arrived home, I put on my pyjamas and I lay down on the sofa. I was exhausted and I wasn’t very hungry.
I need to figure out based on the context what word is missing. My answer is simple - After. Which is wrong. Since I'm not a native speaker I translate the sentence word-for-word. May be that's the problem, because I can't think in English, however, I don't see how 'after I arrived home' can be a mistake.
The right answer is 'as soon as', which means 'when'. 'When' is perfectly fine for me, but why 'after' doesn't fit here. Is there any special grammatical rule for that type on sentences?