It is really interesting that you were not treated at all but you don't have any serious problems. Usually if a child is off diet during developmental years it affects their brain greatly. You may have a more mild form of PKU like hyperphenylalaninemia.
I would suggest that you find a doctor who can officially diagnose you and start a low protein diet if necessary. Nowadays, everyone is all about the diet for life philosophy. And let me tell you, if I start to slip up with my diet I can definitely tell. When my levels are high or I haven't been drinking my formula, I get lightheaded, headaches, fatigue, and have lots trouble focusing. When my diet is good, I feel better all around- mind and body. If you talk to some adults who have been off diet and have gotten back on, most of them say how amazing they feel after their diet is in control. It is a possibility that being on diet is all you need to help clear up your other problems.
I hope this helps! If you have any other questions I'd be happy to help.