I actually went for the first time in 10 years, last year at age 34. I brushed and flossed regularly but I was worried beyond belief to go back for the first time in ages. I can completely relate to the OP. I seriously had anxiety that the dentist was going to freak out about how terrible my teeth were.
I am here to tell you it was surpsingly no big deal. I had no cavities and the whole thing lasted about 20 minutes. He only mentioned a little buildup in hard to reach places and showed me how to brush those areas. I've gone back since. I would be totally cool with skipping a few more years, but I now like the clean feeling that I get after leaving his office.
Looking back, I'm sure the dentist has seen far worse teeth than mine after skipping 10 years of appointments. The majority of people in this world are probably not nearly as anal about brushing and flossing as I am.