Luggage Limit

Hi, I'm traveling from Shanghai to Beijing on the Gtrain and I have a lot of luggage because I have been here for 5 months, and I'm taking it all to Beijing since I am flying back home from there. I am worried that I have too many pieces and that they're too heavy/big. I've rode the train before and I know that there is not much room for luggage in the cars, is there another storage for luggage under the passenger cabins or in another cart? Will I have to check in my luggage (is that even an option?) and how much will that cost?