First of all, be really careful about pinching your nose and blowing - it can actually cause more damage than good if you're not very gentle when you do it.
I found this on the ENTNET website: If yawning and swallowing are not effective, unblock your ears as follows:
* Step 1: Pinch your nostrils shut.
* Step 2: Take a mouthful of air.
* Step 3: Using your cheek and throat muscles, force the air into the back of your nose as if you were trying to blow your thumb and fingers off your nostrils.
* When inflating your ears, you should not use force. The proper technique involves only pressure created by your check and throat muscles.
You might try taking an oral decongestant (pseuodephedrine) right before you get on a plane? Decongestant sprays like Afrin also work well as long as you only use them occasionally (they will cause a rebound effect and actually make the swelling worse if you use them consistently for more than a day or two - once in a while when you fly shouldn't be a problem thought).
Things like TMJ, allergies and sinus problems can all cause your ears to be blocked because they cause inflammation that keeps the Eustachian tube (which is a narrow opening that helps equalize pressure and airflow in your ears) from opening and equalizing the pressure.
Have you been to an Ear, Nose & Throat specialist to have them check out your ears and be sure there's not something else going on in there?