Re: Okay need serious help!
If he only eats one side you could pump the opposite side while he eats (or right after if you can't work the logistics). I wouldn't do it for every feeding, but maybe once or twice a day.
Like the pp said, you don't need to build up a huge stash but since he's only eating on one side it's almost like you might as well. kwim? But keep in mind you don't have to be super strict about it at this point, since you are with him and he's nursing. Once you are working you will want to pump both sides every few hours to keep your supply where you need it.
“We are not put on earth for ourselves, but are placed here for each other. If you are there always for others, then in time of need, someone will be there for you.”