Be careful when flying while sick...I perforated an eardrum years ago (probably the worst pain I've ever experienced), and my hearing hasn't been the same on that side since.

I end up flying with colds and allergy flair ups all the time though now...since I fly for a living, I'd probably be out of a job if I stayed home every time I was congested. A good decongestant is a must - take it about an hour before you fly any time you feel mucous-y. Nasal sprays can be very helpful, too, though I personally don't like to use them often. Obviously, drink a lot of water when flying, whether you're sick or not!

If you have ear block after a flight (that feeling of pressure you describe sounds like it) and you're still unable to clear your ears, you should see your doctor or go to a walk-in clinic. The employee clinic at the airline I work for has a protocol of prescribing high-dose prednisone for ear block - I suppose it reduces the inflammation quickly and helps open the sinuses and eustacian tubes. Not sure if it'd be appropriate for the average passenger, but it's very helpful for us since we're often right back up in the air again after it happens.

Hope you're feeling better by now. Keep some strong decongestants in your travel bag in case it happens again!