Welcome to the forum! I am sorry your son is suffering and I hope he gets the help he needs soon. I know this is hard on the entire family. My daughter is 19, too, and the two of us have been battling this disease for over 3 years, but have had it much longer than that. We understand what you are going through. The symptoms of lyme are numerous, varied, seemingly endless, and "all over the place". You will learn a lot as you read this forum and do your own research. Be prepared for the "long haul"---there is no guarantee of a "quick fix".
It is fortunate that your son's test proved he has lyme. It would also be a good idea to ask the llmd to test him for other "coinfections" such as babesia, bartonella, ehrlichia, mycoplasma, rickettsia etc. and also for heavy metals and mold toxins. These types of conditions often accompany the lyme and will have an influence on the type of treatments given. Sometimes, the more stuff a person has to "battle", the longer recovery can take.
You can start learning about lyme by reading the topic at the top of the first page of this forum, entitled "New to Lyme, Start here". You will find it helpful.
Learn to be your son's advocate and pay attention to his symptoms (keep track, write them down to tell doc). Sometimes it is hard for us to know the difference between a reaction to medication vs. a disease symptom. Lymies can become unusually sensitive to things and it will affect their behaviour and symptoms. I'm not sure if the laughing is a response due to the disease or the meds he is on. Let his doc know.
Our best wishes to your son, to you, and your family, the bablymers family