Writers Block

I am struggling with writing my dissertation and I am not sure why.  I love my topic, I am passionate about it and I am anxious to get to the stage where I get to gather actual data. My prospectus is approved, my first chapter is completed and approved.  Right now I am knee deep in Chapter 2, my literature review, and I anticipate it being about 25 pages when completed.  Twenty-five pages is nothing for me to write, I have written longer papers in a weekend, but for some reason I am struggling.  Right now I am almost done with the first half, and I need to finish the entire chapter by the end of the week to submit to my chair for review.  I know I am 1/5 of the way there with Chapter 1 done, and once I send off Chapter 2 there will be edits and changes, but for the most part I will quickly be approaching 2/5 of the way, but still I sit here and blog and not write.  Ugh.