Lorazepam

Greetings, was given a 10 day dose of .5 Lorazepam to use as need as my recent migraine would not stop and was literally killing me as they did blood work, etc. too. Instantly my migraine is gone. I would not like lorazepam every day, but oh if I could get it as a rescue or preventative if I know my migraine is going to flair. It would be peace of mind that I would not have to suffer for two weeks in agony. Why doesn't it work so well well on my migraine. First day I have been able to function and not be on deaths bed.