OP - YANBU for being worried about it. It's petrifying and the fear of the unknown is damn right anxiety inducing.
Since I have been able to, I have had my smear tests. My Mum however didn't. She would always find an excuse, or generally forget that she was so overdue. She died in October aged 51 from Cervical cancer (well it was the sepsis and kidney failure that killed her because her body was too weak for the second lot of chemotherapy that she chose to have to try and extend her life by at least a couple of months for her 3 children - my youngest brother is 14).
If she had gone for her smears, they would have caught the abnormalities early and she would still be here to welcome her first grandchild to the world (SIL is pregnant), to have watched me get married a month ago and to see her 14 year old son grow into an adult and live his life with both of his parents.
If you are concerned, speak to the nurse or doctor beforehand and see if they advise any preparation that you could do?
If it's embarrassment that's making you worry, trust me, they see hundreds of vaginas a week, yours will just be one of many.
I know my reply has been a bit self pitying, but I am just trying to get the worst case scenario across to you. Good luck as i've seen that you have booked it and WELL DONE! :)