Dude, i feel your pain. I had a 10hr stint once, brutal and gets painful.
Not really suuure what mine was. I was on a decently high dose of stims and TREN...thats the kicker there for me. THE TREN.
For whatever reason, Tren + stims make my core "twitch" or spasm. And i just randomly got the hiccup and they didnt stop.
I do have a trick that a nurse gave me...swear it works and ive told other people the same thing.
Kinda tricky to explain, but i swear to god it help.
Try to suck air slowly into your lungs...but do it like your sucking thru a straw....slow and steady.
When your lungs get full, take almost sips...quick little sucks (thru a straw...) trying to get the most air possible in.
She explained that this is stretchingggg your diaphram, which helps kind of stop the spasming and hiccupping.
So keep sucking and when you cant take anymore more small sips of air, holdddd.....and try to count to 15.
This works for me 9 times out of 10. The "stretching diaphram" thing makes sense