Thanks again for your reply!
Yes, I did have migraines when I was a child. (I was very light sensitive and it were bad headaches when I got these migrain attacks.). I did not get the migraines anymore when I got older (actually I have not yet suffered from a single real migraine attack in my 20s)
I've always been sensitive to weather related headaches, too. Put me in an unairconditioned car in the summer and you would get a 100% garantee of me getting a headache. This also got better when I got older but I've been still experiencing it as I wrote before so not like the migraine that was gone at some point.
Maybe I've been set back in this aspect due to the concussion (somekind of reactivation of headache activity) and the history of headaches makes recovery prolonged in our cases.

Also, please keep in mind that your son "just" did not rest for 3 days. Be patient.

Thanks again for your reply and thanks for naming the supplements brand.

Now, I'll really be offline and not checking back this board for some days because of strictly not using the computer in order to rest.
Thanks to you and to Mark for replying!