That's an awkward age with hormonal changes, a potential voice change, seeing all of one's friends start to drive, trying to fit in socially, living a 'clean' life without smoking, drinking, and many other stressors. Personally, I escaped into my music, reading, art and math (weird, I know). I was treated differently by some students and teachers. Some were over-protective, some were nonchalant, and some were downright discriminatory. Some were simply accepting of the epilepsy. He's probably had some of these emotional experiences over his brief life. I had a dog who was my very, very best friend on both good and bad days.
Maybe he can try the gluten-free diet or look for food/drink without some of the additives like caffeine, ginkgo biloba, ginseng, just to name a few. Some people in here strongly believe in neurofeedback. It may help him as well.
At that age, I was on Dilantin combined with phenobarbital which worked pretty well, with the exception to the occasional flu that I'd get from others. Personally, I strongly feel in favor of brand name only medications.
There is the possibility that he has experienced 'kindling'. Once one seizure starts, it takes a while to prevent the next one even if one is faithful with medication. It's like a storm that eventually slows down again, but it takes a lot of patience. For me, that would last for an average of one week.
It's a catch-22. If he worries about that next seizure, that stress could actually cause another seizure. It becomes a vicious emotional cycle. I'd suggest that he listen to soothing music, or find something that helps him release his stress.
My new stress relief right now is an intense workout with strength training alternating with brisk walking or 'cardio'. There are stress hormones that just wreak havoc with epilepsy.