Guardian ad lietm ?

Doesn't the guardian have power to write to the judge and make recommendations if appointed in your state?  Who does the child reside with and what type of custody do you have?  This makes a big difference.

From my experience because I have two children classified with ADD and my ex has done the same thing I have gotten letters from their doctors saying their condition and why they need the medication.  I have provided my children's IEP's from their respective schools and made a motion to the court that if a recommendation is made by a qualified doctor than my ex has to follow the recommendations.  In my motion I had it court ordered that if he does not attend any appointments or Child Study Team meetings he has no say in their treatment and he is not allowed to call anyone of these professionals and use improper language. 

I would consult with your attorney about all of this, since I live in New Jersey and the law might be different in your state.

Thank you so much for all your imput I really appreciate it!!!!

The GAL is the best thing that could have happened to you. This person is going to see the clinical diagnosis and FORCE your ex to comply, or risk his custody/visitation.

I realize it is hard for some parents to swallow the idea that there could be something "wrong" with their child that needs medication to control. Heis going to have to accept it - the court won't allow him to not do what is in the best interest of the kids to cover his pride.

They are trained to see problem areas. Working with kids is what they do! They will speak with both parents separately- and also to your son.
As for the meds - make sure his lawyer is aware. Go armed with contact info from his Dr and from the counselor. Call BOTH of them and make sure they understand they have your permission to share your sons info with his lawyer. I would make sure they are there to testify also!
 He is trying to turn your son against you and it appears to be working. Don't be frantic- don't talk to your son about his dad doing this- keep your cool. Be careful what you say! It may be used against you later!
Document all instances and date it. Have all of this info ready for your sons lawyer.

My guess is that is the same as the "law guardian" who was appointed to my children in NY state.   
She came into the house, tried to view the dynamic of the household, talked to the children alone.   My ex and I each had a chance to speak with her separately and express our concerns before she ever talked to the children or come into the home.  I would bring up your concerns. 
To me, from what you're saying, it sounds like your ex is in a lot of trouble.   But you need to keep pressing the issue and make it a high priority.