I am glad husband took him to the ER. With his history of migraines, it may be time to find a neuro who specializes in treating migraines. I know you had one a couple of years ago who didn't do anything, but there are a lot of neuros out there and I am sure that you can find one who will help. In the time before you can see a neuro, get the doctor to trial various triptans to treat teh headaches. PLEASE don't have him take excedrin migraine or the like. If I remember difficult child's past headache pattern, he will likely have quite a few in a period of a few weeks or months. If he takes OTC medications like those headache powders or excedrin (excedrin migraine is just excedrin with different packaging and fewer pills for more money - very small difference in the actual ingredients), he will get into the rebound headache cycle where he takes the medication, it helps the first time, then he gets another and takes it and soon it isn't helping much or he is taking it 3 days a week or more and then his body will get headaches because it thinks it is supposed to ahve the OTC medication. At tat point you are really messed up. You have migraines that are not helped much by the OTC medication, but they are triggered by not having the OTC medication in the body.
So he NEEDS actual prescription medications to treat this. It is EASY to get into the rebound cycle with OTC medications (even just plain ibuprofen, aspirin or naproxen can and will do this to him in less than a month's time - been there done that and it is UGLY and PAINFUL to get out of that cycle).
A doctor, even the family doctor, can start him on a beta blocker for prevention and give an rx for a triptan. It can take time to find the right preventative and the right triptan. Just because one doesn't work doesn't mean another won't, esp with the triptans. Also be aware that some triptans work better with naproxen (aleve). IF taken only with the triptan medication, it is OK to take ONE dose of the naproxen IF IF IF the medication doesn't have naproxen in it already. With the triptan you are likely to NOT get into that rebound cycle. YEs, it is contradictory, but the naproxen added tot he triptan will make the triptan work better and you don't take as much naproxen as if you were using it alone. The migraine medication treximet is simply imitrex and naproxen. Keep that written down and if the doctor wants to rx treximet ask if you can have an rx for generic imitrex (TONS cheaper!) and a note for school that difficult child has to take 2 aleve with the imitrex when he gets a headache. You can save a whole TON of $$ by doing this - and some ins co's won't pay for treximet because it is imitrex and naproxen.
Even if the family doctor is okay with helping to find the right preventatives, your son may need a neuro to really figure it out. A chidlren's hospital may be the place to find one, or he may qualify for an adult neuro, it just depends on the neuro.