OK, for severe insomnia, you have to have the "sleep promoting" circuits in your brain working hard, while suppressing the "awakeness promoting" circuits as much as possible too.
There is the obvious, low stress, exercise earlier in the day, being (reasonably happy and content), having sex before bed (or masturbation if you don't have a partner). Good massages and a good chiropractor. Avoid sweet foods as much as possible.
As far as drugs go, you've also the option to cover multiple bases:
1. Histamine, awakesness promoting NT, so you use antihistamines, like Diphenhydramine.
2. Acetylcholine, many functions but also awakeness promoting, anticholingeric drugs are known to be sedating, Diphenhydramine will also do this at higher doses, as well as various TCAs (beware any type of antidepressants though as they tend to have a net agitating/energizing effect.
3. Serotonin, again many functions but it is known that antagonism of 5HT2a receptor in particular is responsible for strong anxiolytic properties of drugs that antagonize 5HT2a. Here we have quite a few, quetiapine and olanzapine. Both drugs bind first of all preferentially to histamine receptors, and olanzapine has some wide ranging anticholinergic effects as well. Both drugs, again olanzapine a lot more, antagonize 5HT2a receptors and this in addition to histamine and acetylcholine which is responsible for its positive effects on sleep.
4. Dopamine, again many functions but D2 receptor antagonism tends to exhaust you of energy, of drive, it blunts some people. But it is relaxing to take before bed.
5. GABA. Benzos act on GABA receptors, but as you can see from above, it's just one of quite a few methods of putting yourself to sleep.
What my friend does is take Diphenhydramine at a high dose of 200mg, first of all. This allows the DPH to saturate histamine and acetylcholine receptors. So now you choose an antipsychotic, say olanzapine. It is usually very strong at histamine receptors and starts on them first, but if you've blocked them all with a much cheaper alternative in Diphenhydramine, the antipsychotic should then default to the next preferred receptor types. So, if olanzapine, for example, prefers Histamine and Acetylcholine receptors but they are all blocked already, it will start to do other stuff, like 5HT2a antagonism, and dopamine antagonism, both very calming and sedating in addition to the antihistamine and anticholinergic effects of DPH. One may then diversify by calling on benzos to finish it off. Obviously faster acting benzos would be preferable, because the other drugs should keep you asleep so it doesn't fully matter if it doesn't last all night. Midazolam 15mg or Triazolam 0.5mg are excellent for this function. Since these are hard to get, one may opt for tems, cinolazepam, or whatever short-intermediate acting benzo you can get. Heck, dia can do the job as most of the "action" comes only for a few hours, almost like a fast acting drug. Clon on the other hand is barely noticeable even at higher doses, that is until you go out in public and you find it easier to talk to people. Even with dia, the above combo is nuclear, really powerful. If I had to take Ambien on its own I wouldn't sleep, so don't beat yourself up about it. Find a way around it.
Intended for informational purposes only. This is not medical advice.