iPhone X dies fast while on Facetime

Does anyone else have a problem where their phone (specifically iPhone X) dies extremely fast while on facetime? Also, when I'm on Facetime and I'm charging my phone, my phone doesn't charge. Like when I plug in my phone it shows that it's charging with the little bolt symbol, but the actual percentage number of my battery is decreasing. Why does this keep happening? And why is this happening while I'm on Facetime? Thank you for all your help!