ACL/MCL tear or meniscus sprain?

I fell while going for a dig during an indoor volleyball match. Of course I was wearing my kneepads but lost my balance and went down on the inside of my knee instead. Thus, falling on my knee and hearing it pop. I scheduled a Dr. visit and to sum it up, without an MRI there was no way to tell immediately which injury it is. She treated it with a knee brace and said that if the pain was no better in two weeks that it's probably a tear. So it's been two weeks and here Is the lowdown: knee has some fluid around the inside of the knee and some on top around the patella. I cannot rotate my knee AT ALL. And cannot straighten my leg all the way. I cannot lightly exercise (walking). What should I do and which injury does this sound like?