Need some ACL help/info?

After running my frst 50 miler, I started to have knee trouble. I eased up on the running and started the elliptical/swimming but it just wouldn't go away. I went to the doc and got an MRI. While no stress fracture showed up, they thought I had a very early one on my tibia- since there was bone marrow fluid there. They also said my ACL was bruised.

I did NO leg exercises for 4 weeks, as my doc prescribed. I swam (pull only) to stay in shape. I have now gone back to the elliptical. It does not hurt while I elliptical. My knee doesn't feel better... kind of "weak" if that makes sense. Which I don't get- it feels exactly the same as it did 4 weeks ago! (except it used to hurt when I ellipticaled and now it doesn't, so that is good)

Today I ran to the stop sign and back (.00001 miles lol) and it hurt RIGHT away, so I am not ready to run yet. I'm just wondering, do you think it was my ACL that was causing that pain? And if so, is there any stretching, etc I could do that would maybe help? I kind of feel lost on what to do next. If I have a plan, I can start to feel sane again.

Thanks guys!!