Speech Problems

Hey, thanks for taking a look at my question.  My son has severe OCD, anxiety, major depression, panic attacks.  He was place on Prozac.  Took it for almost 2 weeks.  He began stammering, becoming unable to communicate and his body became so un-coordinated, with staggering/shaking, that the doctor took him off--no meds for another 2 weeks.  I took him to another doctor who placed him on Lexapro 20 and Seroquel 600.  The body shaking has pretty much stopped, just slightly when in public setting.  However, he has not regained his speech.  He can say one word answers, with a great deal of difficulty. This has continued for almost two months now.  What is strange, is that on two occasions, he has cried, and then been able to regain his speech for a day or so, but then looses it again.  Any information would be helpful.  Has anyone experienced this?  What helped?  Is it medicine related or emotional, or both?