High C and High D aren't unreasonably high notes, particularly for someone who can scream out double A's.
Sounds like you don't really own a high D and are trying to force it.
My knee-jerk reaction is to assume that you don't practice/play enough, which means your chops aren't strong enough to do what you're asking.
Practice/play for several hours every day. Keep it under high C for a while, then move up.
Time is a wonderful thing if you use it to practice.