Cavities

Is it normal to get cavities? And what does it feel like? I’ve never had one before but I think I may have 2. Idk if I should be worried or not. I feel like I brush my teeth pretty regularly but I do have very sensitive teeth so maybe I’m not cleaning them enough if I do have some. There is some brown spots on my back molars. Idk if it’s a hole or stain. I do have some pain but my wisdom teeth are coming and I will be getting those out next month.