Flonase and headaches?

I know it's listed as a pretty common side effect, but wanted to see if we had any real-life experience here.

I started taking it on Monday night, hoping to head off the December/January cedar pollen allergies here before they start. I had a mild headache on Monday (before I took it) which I attributed to not getting as much sleep as I did over the holiday week. Woke up Tuesday morning with a more mid-level headache that eventually went away. Then Tuesday night I slept restlessly as I had a headache and since I woke up this morning (about 5.5 hours ago) I've had a pretty awful migraine. There's no other identifiable cause that I can think of. I'm in pretty dim room, I've had caffeine and taken what meds I can take, and nothing is helping yet. (Yes, I'm a chronic migraine and headache sufferer, so I'm not worried about something freakishly weird or anything.)

So, wondering if Peas have had similar experiences at all, and if so, did the side effect go away after a couple of weeks of use? It does seem to be helping from an allergy standpoint, but I can't keep using it if this is going to be my every day!