Baby is silent

My 4.5 month baby is very silent for past one week. She is literally mute. And sound is coming when she is crying. Before that she laugh out loud and full of fun. So active. But now she is silent not very active and smiling and no sounds at all. Any thing to worry. Sometimes she straining as if she wants to poop.. but not pooping.. she is chewing always like she is eating food. #advicepls #firstbaby #firsttimemom #babyworry