It's sinuses. Basically, you're the telltale reason why people don't go diving with a cold. The change in pressure causes the pain. Your sinuses have one pressure and the air around you has another. They don't get equalized and that's what causes you pain.

I'm not sure what is causing your congestion, but talk to a doctor or travel doctor about it. People here have suggested allegra. That's great if you have actual allergies, but it doesn't treat the actual congestion. It moreso goes after the antihistamines in your blood. You're better off taking something like actifed. It dries up your mucous membranes. Stay away from mixing different allergy medicines too. You could end up with a headache making you cry as well.

Long story short though, ask us here about upgrades, seat assignments, etc, and leave things like this to medical professionals. Talk to a doctor about this and chat with a pharmacist about the drugs you get.