"Terrible insomnia" means having extreme difficulty falling asleep or staying asleep, which can cause a lot of frustration and exhaustion. Full definition
I was always breaking down, and had several attacks of what is called nervous prostration, with terrible insomnia, being on the verge of insanity; besides having many other troubles, especially of the digestive organs. (religion-online.org)
For the last six months, Cero, a painter, had suffered terrible insomnia. (myintimcity.com)
Well, the week or so passed, and one night I had terrible insomnia. (bylaurenm.com)