Hello! Could you please tell me how to understand what is called "tonu…

Hello! Could you please tell me how to understand what is called "tonus"? Only by a doctor. I have strange sensations - light tingling in my belly and like muscles ache after training. There's no more pulling. Just as I read, it seems that tonus isn't like this. But it's my first pregnancy, maybe it manifests like this. Please tell me ?? I am very worried and start to overthink: I don't want to lie in the hospital.