Mayo Clinic is a fantastic place to start!
The most difficult part is of course all of the waiting you have to do when you are trying to find a diagnosis during the early years. I think this is because there is no true "timetable" of development. We know the average time that certain milestones are supposed to occur. But this is never written in stone- a child that hasn't hit a specific milestone (like standing) by a certain point will most likely have difficulty reaching their next milestone (like walking) within the average age range. Many children have uneven developmental profiles- language skills may be quite advanced, but fine and gross motor skills may be behind. This adds to your frustration most certainly because you want to know the reason WHY, and also makes diagnosis take a little longer. But this time is important! You need a proper diagnosis. You don't want somebody to jump to conclusions.
Finding the right clinician is definitely important. I look for someone that works well with my child. I look for someone that is open minded and easy to talk to. I don't want to be rushed out of the office before I have had a chance to tell the whole story. I also need someone that has the patience to explain their findings and tell me the next steps. I also want to know that I can go back to them if needed over the course of my child's life. In our journey we have had a mix of clinicians. Some have been fabulous and some have been less so. I like the ones that take the time to answer my questions, or if they can't, direct me to someone who can.
To borrow the words of a friend, "A mother may not always be right, but they are rarely ever wrong." If you feel that you have not yet received the right diagnosis, it is important to keep pursuing it. 🙂
My son has hypomyelonation in certain areas of the brain. It is believed to be part of his genetic anomaly, although he is pretty rare. No one else has the exact same genetic blip so we don't know for sure. For him, the comparative MRI's done about 2 years apart showed no change. This is a potentially upsetting result for many but we embraced it. We may not have "fixed" it but he continues to grow and develop and that makes it less frightening. It may also mean that the pattern of hypomyelonation that he has is not a bad one.
I wish you much luck on your journey. Should you ever need to chat don't hesitate to contact me. Mama's need all the support they can get!

Xoxo

Keep us posted!