Why he does something like that?

Lately my boyfriend has been distant and we don’t talk almost at all.. The past 3 days, when he calls me, after a short time he says hold on I will call you back and he doesn’t call again.
He wasn’t like that before, when he used to tell me I will call you back he used to call.
What’s wrong with him? Why he is doing that? I don’t want to ask him because he knows what he is doing.
Why he does something like that?
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