When do you know your CH phase is starting?

I've been having really bad shadows, pressure in my head, having to pause and breath through the pain and preasure now and again, sensitivity to light, extremely tired and irritable. I go on a week long trip overseas by plane from tomorrow for work and I'm worried...I'm not sure if I'm just having a 'normal headache' which I basically never get!

For context, I get 1 or 2 CH phases a year and do randomly get shadows but I feel like I don't have phases enough to understand if it's coming or not idk. I guess it's just hard to tell.