need some oxygen tips

Been using o2 for ages and all ok. but last couple of weeks been getting hit hard with clusters, not severly strong but on/off all the time.

Using the demand valve o2 which has very quick success everytime but the next cluster hits between 5min-an hour after the o2.

with the normal o2 used 20+10 mins to prevent reoccuring, but cannot manage 20 mins on demand o2 get too sleepy and breathing in getting harder.

gave o2 a miss for a week, but still the same problem again today.

[also use imigran jabs max 2 a day]