Doc,
Off label use of Gabapentin (Neurontin) works for some Ch'ers some of the time as a prophylaxis/preventative, but burn-through becomes a problem after a few weeks for most and that requires increased dosage to achieve a therapeutic effect.
I tried it for nearly 6 weeks but the side effects... 2-3 Martini Buzz (not cool when driving) and swelling ankles (required too much hydrochorothiazide as a diuretic) so I bagged it and stuck with high flow rate oxygen therapy. That was 5 years ago and high flow rate oxygen is all I use... It's very effective if used at flow rates that support hyperventilation. It's also very safe, far less invasive, and a lot less expensive than other prescription medications for cluster headaches.
I've got a few years on you and spent the better part of my youth sucking down copious amounts of 100% oxygen flying Navy fighters at very high flow rates... I've a total of over 3000 hours worth of flight time and all was spent breathing 100% oxygen on missions lasting two hours or more in length... I'm still here.

Ping your neurologist for a prescription for oxygen therapy.
Your prescription should look like the following:
"Oxygen therapy with a non-rebreathing mask as an abortive for cluster headache pain. Administer at onset of attacks at 12-15 liters per minute for up to 20 minutes per hour, up to 12 times per day. ”Notes:
1. Most prescriptions for oxygen therapy must be renewed every year. Play it safe and have your physician add “Refills for one year” to the above prescription.
2. Pulse oximetry and arterial blood oxygen are not required for approval of home oxygen for cluster headaches, but you may need a certificate of medical necessity (CMN) signed by your doctor.
3. Have your physician specify M-size oxygen cylinders for home use and E-size portable oxygen cylinders for work and local travel. These two types of oxygen cylinders require different types of oxygen regulators.
4. Obtain a paper copy of this prescription for your records. It will come in handy if you go on travel and need to order oxygen when you’re away from home. If you don’t had a copy of the prescription, the monthly receipt from your home oxygen supplier will also work while you’re on travel as it provides proof you have a current prescription for oxygen.
5. The sample prescription above is written for a maximum flow rate of 15 liters/minute because that is the highest flow rate supported by present clinical studies that medical insurance companies will cover. Accordingly, that is the maximum flow rate most doctors and neurologists will prescribe.
Although you will need a higher flow rate, 15 liters/minute is far better than nothing and it will get you started. Having said that, don’t be afraid to ask your doctor or neurologist about writing the prescription for 25 liters/minute insisting that this flow rate is perfectly safe and far more effective. High flow rate oxygen regulators (≥25 liters/minute) can be ordered over the Internet without prescription.
Take care,
V/R, Batch