The eyes are indeed the mirror of the soul, as an old saying goes.
It would be different if you could stand to watch people in the eyes and you found it easy but decided not to for a number of reasons.
For some reason, you seem to fear getting to know other people and have them know you. This may be conscious or unconscious. This is what it seems to boil down to, deep down. Interesting would be to know the answers to the questions asked by Larissa. Regardless of the answer, being shy/introverted/socially akward or whatever term you want to use is not a mental illness, contrary to popular opinion. It becomes a mental illness when this trait is so strong that it becomes debilitating to your life. For example:
• you never leave the house because you don't want to be around other people;
• you don't look for a job or don't go to interviews for fear or shame of having to deal with an interviewer (in case you don't have a job);
• you have a job but you start not showing up at your workplace because you don't want to interact in any way with your coworkers...
etc etc If a trait is so strong that it can compromise your survival, than it is a mental illness. Otherwise it just may be a weakness or a flaw, but not a mental illness.
Another question you should ask yourself is the following: "Did something happen that affected you and makes it difficult for you to look other people in the eyes?"