Is my stepson jealous because I'm pregnant or not?

Yesterday while we were celebrating Christmas with our cousins and family, I surprised them about my pregnancy including my husband. They all were so happy and my husband couldn't believe it. My stepson was very quiet and didn't give any reaction and after a while he went up to his room. His father and I talked to him about it and he didn't give us any reaction which is weird. If he is what can i do to make him feel better?
P. s he is 13 yo.
Is my stepson jealous because I'm pregnant or not?
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