Yesterday I had to have a full look over in the nude by my dermatologist. I wasn't expecting it and I was mortified. All I could think of was how ugly my body is and how gross I must look. In reality I know I'm thin at 127lbs and 5'8. there's nothing strikingly horrible about my body but I hateeee being in any state of undress in front of people. Is that normal?
What a person considers "normal" depends on the input he or she gets from family, friends, society, etc. In some cultures, nudity is the norm, in others nudity is completely unacceptable. "Normal" for most people falls somewhere between the extremes. Some people are so far to an extreme that they will not even allow their spouses to see them naked. Others have no problem appearing nude in acceptable public places, like nude beaches. Whatever works for you (and your spouse when you marry) should be just fine, except you should probably work on being more comfortable nude in front of your doctor. If you are overly modest, you have no need to show your body to the public. But your doctor will need to see you in different stages of undress at times.
BUT - you do seem to have issues with accepting your body. You say that there is nothing strikingly horrible about your body, yet you also say that you think your body is ugly and it looks gross. I really doubt that. From the sounds of things, you have bad thoughts about your body, but it is actually fine. Chances are it is average or maybe better than average. I hope that you can learn to accept that your body is fine and be comfortable with it.
Nudity is normal but shame about nudity is normal too:
It's learned trough education, normal education in a part of the world. Since many people are educated that way it is not abnormal but most people get over that part of their education in a number of circumstances: showers, locker rooms, relationships, marriage and in front of doctors or paramedics. An immense part of the population will go skinny dipping if the circumstances are right.
Remember that a doctor sees many patients a day, 5 days/week = more than 220 days/year.
Just calculate how many naked bodies a doctor sees in 10 or 15 years. (do the maths and you'll be astonished)
You're just one of the many. Your doctor has seen it all, many more times than he ever wished for. He won't judge, just like when a mechanic looks at the engine of your Ford or Chevy: will the mechanic judge?
It's certainly understandable, because you probably feel people are going to judge your body, especially when you're baring out everything in the open. Learn to love everything about your body, even your perceived "flaws" and you'll eventually realize that it won't matter.
It's completely normal everyone is like that about their body. The best way to feel more comfortable about it is to get naked more often in your room and get used to your body. It helps when you have an image of how you look when you look in the mirror.
It is too bad we do this to ourselves. I started going to a nude beach. First time was by myself. What a great experience being nude all day with other people. There is nothing wrong with enjoying being nude.