Hey dreamers

Every time I become lucid and try to think about where I am in relation to the real world I will get a horrible headache in the dream. For example last night I was in a dream and I was trying to figure out what the day was. I told myself in the dream that today was November 15 2010. My dream however when I tried to concentrate on this fact wanted to believe that it was August 15 for some reason. When I concentrated harder about where I was sleeping, what I had done yesterday, I get a realy bad headache.

This has happened before. What should I do? Should I try to fight the headaches and continue concentrating on the outside world, or should I just not fight against it and let my dream take over?

Also does anyone else experience this?

p.s. - I am on celexa, which might have something to do with it.