Your sensitivity to altitude changes indicates your Eustachian tube is not opening normally with the pressure differential between atmospheric and that in the middle ear. I’ve had this problem off and on for decades, particularly on one side. Two things have helped me to get those tubes opening, after recovering from a cold: pseudoephedrine, 30 mg tablet, taking one or two every six hours or so. It’s a vasoconstrictor and decongestant and helps open up the tubes, but it may take a few days. There are the side effects of making you a bit jittery. After a a day or two, try to “pop” your ear, i.e., pinch your nostrils to force air through the tube into the middle ear (equalize). If you’re not familiar with this, ask your ENT specialist, and be careful; it only takes a tiny amount of air. One thing I discovered in desperation while scuba diving and not being able to equalize: if the trouble was on one side, I could equalize more easily by bending my head down towards my shoulder on the opposite side, before popping. I don’t know why this works (but it also worked for a friend who was having trouble equalizing after a plane flight), but I might be stretching something near the tube, but it worked. Now as your working on the tube, pop your ear several times a day; this helps get it opening properly, and will work together with the pseudoephedrine, which may become unnecessary.