My boyfriend doesn't answer me for 3 days?

last time he sent me a good night message on Saturday
On Sunday i sent him some ouc and wished him great Sunday he didn't answer but read it
On Monday i sent him messages he didn't even read it and seems like he wasn't online
Today, he wasn't online whole day
i called him on Monday he didn't pick up his phone
WHAT IS GOING ON?
My boyfriend doesn't answer me for 3 days?
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