Stories, too many to write, too little time

Well, this summer, I've been writing a story continued from the series started by my friend and I. So far I've gotten three little itty bitty chapters. I want it to be long, and yet I just can't seem to put enough detail. The plot just moves. It doesn't like to slow down, so it might not be as long as I would want. Oh, well, I will just try to write it however it likes. Then I get to write another one. How incredibly fun.