One more thing that complicates identifying triggers...we are relying on 15-year-old girls for our information. Here is how our conversations go:

Her: My head hurts.
Me: I'm sorry. When did it start?
Her: I don't know...maybe 3rd hour.
Me: Were you reading, or...
Her: I'm fine.
Me: Did it hurt all day? (silence) Or was it one then and one now? (silence) Do you want some Tylenol? (silence)
Her: Guess what Matt did today at school?

Once in awhile, like maybe once every two weeks, my daughter will concede to a full inventory of how many symptoms she's having, what might be making them worse or better, etc. I thinks she's pretty honest and open during those inventories so I try not to get freaked out by the short conversations.