For some people, side-switching might indicate a change in the cycle. For others, it's just another thing that happens. It's not common, but not super-rare.
What jon said -- you want oxygen for stopping your attacks. The more you use the injectable sumatriptan, the worse things are likely to get -- more, longer attacks, longer cycles .... And prednisone should be limited to once a year (a taper of two or three weeks). And the amitriptyline is, indeed, probably useless.
Get oxygen (Read about that and other things here: https://clusterbusters.org/forums/topic/6213-basic-non-busting-information/)
For now, split the injections when you use them: https://clusterbusters.org/forums/topic/2446-extending-imitrex/
Start the vitamin D regimen, which has helped many hundreds, if not thousands, of people with CH: https://clusterbusters.org/forums/topic/1308-d3-regimen/
Consider busting: Read about it at the end of this file -- https://clusterbusters.org/forums/topic/6213-basic-non-busting-information/ -- or by cliclking on "New Users -- Please read here first" at the top of any page (in the blue banner).