I completely sympathise with you. Had my first smear on the 1st of august. (Age 24) Was told the results usually come back in a couple of weeks..had a doctors appointment a week later for something completely different and was told your results are back sooner than anticipated and they are borderline abnormal with high risk hpv.. I then had to wait for the letter to come to me 3 DAYS LATER I was then referred to make an appointment for a colposcopy. Had it on the 13th.
Like you I was terrified.. I brought my mum with me for some comfort. (Might help for you to bring someone to put you at ease)
Once you're in there the nurses/doctors know that this isn't a nice thing to go through so they do try everything to put you at ease. The best advice I can give you is not to get uptight..thats when it gets uncomfortable because your body is then in a tense state (easy to say relax-i know) but honestly it's fine you will be talked through it all and there is a monitor next to you so you can see everything that's going on. If they need to take a biopsy there's a short discomfort but nothing to bad. But some woman are different depending on pain tolerance.
This and other forums have really helped with this process for me as I too suffer quite bad with worry so you're on the right site.