Why is he poor in communication?

So please can someone help me understand why my boyfriend is very poor in communication... so every time i call him he will sometimes not pick up probably he would be busy but him not calling back when he finds my missed calls doesn't sit well with me and his done this several times... and how does a man go the whole day or days without communication unless i initiate... one time he travelled he couldnt even text or call to say his started off or rather his arrived to his destination i tried to reach out just to find out if his safe but he didn't pick up or call back... i did confront him but his not finding any problem with his actions, as at now i haven't spoken to him and he also hasn't spoken to me its been 4days now, am so confused what should i do...
Why is he poor in communication?
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