My cat is getting bald by her ears,on the side of her belly and the back of her legs. Should I worry?

Li
My cat turned 1 years old April 15th and she has always usually had a huge bald spot by her ear but now on inside of her right and left leg it's getting really bald and around her butt! On the left side of her stomach she's losing fur.. My dad's dog does tend to nip her when he gets hyper and wants to play but nothing to be able to make her like this.