Massive headache

[rawstrength]

I just got over having a massive headache . . . I'm theorizing that it was caused by one of three things. Has anyone experience anything similar, and/or what do you think caused my headache?
1. Refined sugar
I had one TINY bite of toffuti (vegan tofu ice cream) last night, but otherwise was eatin 100% raw. It was my first time having refined sugar in a long long time, but I don't think I had enough to set off the major headache that I had. I only ate like 1/2 tsp. and didn't even like it.
2. Wheat grass juice
I had my first glass of wheat grass juice this morning. I took 1/4 cup of juice in 1/4 cup of water on an empty stomach. I've heard that wheatgrass can cause headaches because it is so detoxifying. Should I have started with less juice?
3. Lack of food
I've been eating a lot less lately. I just haven't been hungry. I used to get huge headaches from not eating when I was anorexic ( I know I know, I'm better now) but that was a different kind of headache.

What's the diagnosis? I want to know what caused my headache, 'cause otherwise I've felt great on raw and I want to keep feeling good!

[sport]

I can not say what the cause was but I do think that a quarter of a cup of wheatgrass juice is a lot to start off with.
I take it every day but think that that much would make my tummy ill.