You poor thing - good luck for tomorrow.
Just to reassure you about the procedure, I had a colposcopy last week and although a little undignified, it was fine.
I was thinking cervical erosion as well. If you do have abnormal cells the will be able to find them during the colposcopy (they paint a solution around which highlights them). I have some which they are removing after the birth, but the doctor did tell me that they can remove them in the final trimester if needed.