10K and failed run

On Thursday I ran 10K in 1hour and 28mins.  Near the end my right knee started bothering me.  I didn't think much of it as I thought I just landed weird.  We were out of town Friday and today, but when we returned to London tonight, I decided to get a 6K run in.  Well I got about 1/2K and my knee started hurting.  I walked a bit, tried to run a bit more, but the pain started up again so I turned around and came home.  I have a 20K run tomorrow morning so I am a little worried that I may not make it through.  I did some research online and I think it may be an IT Band issue.  I iced my knee when I got home and foam rolled.  I always seem to injure myself some how when I get this far into my training.