Something similar happened with my boyfriend and I a while ago, it turned out I had said something to upset him. He might not be cheating on you, he honestly might be upset about something else entirely. However it is highly inconsiderate of him to not answer any of your calls and leave you in the dark while making you feel anxious. If he’s not communicating with you clearly it’s immature of him and I would have a serious conversation with him about it or maybe consider leaving the relationship.