Is there a reason why he hasn't done a sleep study for more than just the basics watchings? while night time allergies can play an effect in sleep loss, or sleep quality lowering, the antihistimine isn't going to help with the being able to be alert and awake during other hours of your day.. and after prolonged use of them, it can start causing a person to have brain fog during the waking hours.

there are more than just the sleep studies they can do too. I can't remember what test they did with me after the sleep study but it was a 4 letter something.. maybe 5. it started with a M and there were an R and a T in there somewhere.. but that test was done after the sleep study between 8am-1pm. I'm sure there are other tests too that could be done.

I'm diagnosed with sleep disorder nos, and hypersomnia. the sleep disorder nos, is that i "never ever, not even once, through any of the tests, went into the REM cycle sleep stage", and the hypersomnia he said "means your really sleepy. and in the tests, an average person falls asleep between 10-20 minutes, whereas you fell asleep between 3 and 7 minutes each time" (that test they did after the sleep study).

Stimulants are the only thing that help with me. literally most of my medication are to wake me up, and keep me awake during the day, and then to put me asleep and keep me asleep during the night. I drink a lot of Red Bull energy drinks as well (mainly when my stimulant (generally add/adhd type of meds) is too low of a dose).
Sleep deprivation can come even if you are sleeping. its the quality of sleep that matters. and if your waking up sleepy, or sleepy through most of the day, it's likely due to the quality of sleep your getting is lacking. Which can worsen almost any other illness.
There's only been 2 days out of my entire life that i've woken up and was awake.. once in high school, and once a few years ago. and i was almost borderline of being hyper those two times. otherwise, i wake up, and lay there.. thinking that i might fall back to sleep.. and usually I do.. but i wake up, and i dont wake up being awake, I wake up being ready to sleep again. feeling just as i did the night before i fell asleep.

Was the sleep specialist a neurologist? (mine is a neurologist).
The diet thing that Perna mentioned is a good suggestion too (along with the other suggestions), but if you eat too much sugar items, you'll crash, and might not feel so great when you wake up (high blood sugar).. if it goes up real quickly, it will go back down just that quickly.
Starches and greasy foods also can cause sleepiness.