Exercise Triggers?

So, I read exercise is a trigger, and I have a problem. My migraine medicine makes me hungry. Migraines make me hungry. Plus I really like exercise. So not only do I have calories to burn from my migraine induced diet, but I really enjoy exercise and it solves a few nonmigraine problems. One problem being female cramps that are debilitating when paired with a level 5 migraine or worse. I actually had to miss school because the two combined plus the effects of my meds made me unable to function.

So, you know that I like to exercise, and are starting to figure out my concern. By all means, exercise is the best course of action for me in my opinion, but it might be a trigger, which isn't a good course of action. I was wondering if there was any way to tell without going straight into my full-out exercise routine (45 minutes of ab workouts).

I've been thinking about this, and during the week is when my migraines are the worst. When I'm on break or don't have class, I'm fine. Well, what's different during the week vs weekend and break? For one, I'm visiting family. So maybe being in a different area with different climates might be a factor. Another difference is I walk A LOT at school. I just do. I could take the bus there, but I like the walk. It's good for me knee (which also has pain). IT gives me time to think. IT's good for stress. Lots of good health benefits for me.

Could the walking be a trigger for exercise triggered migraines? Is that a sign? I really want to make sure that exercise isn't a trigger before I get back into my old routine, but since I'm in relatively good shape, it takes a lot for me to feel a burn. At what point is it considered exercise, and how do I test the exercise triggers?