I have quite a few cashmere sweaters. I don't wear them often anymore, unless I go out somewhere, but I used to wear them to work all winter long.
Mine have never pilled, except for one. It was an Issac sweater from QVC and very thin 2-ply cashmere. I kept it, but it was not as nice as my other ones..not even close. I always get my cashmere sweaters dry cleaned, so they stay nice. I have cashmere socks that I wash. They get pilly, but they are warm.
Maybe you have an angora sweater or angora is mixed in. Now those sweaters pill. I once had a beautiful red one. At the end of the day, my bra was red. I had angora stuck under my armpits and my chair at work was red too.
The whole sweater was full of pills. No angora for me..ever.