I have really intense ear pain during descent in commercial flights. Would it be better or worse if I was flying a small non-pressurized plane?
Commercial airliners are generally pressurized to a cabin altitude of around 8000 feet when at high altitudes. So it depends a bit on where you live. If you live near sea level, you're feeling around 8000 feet of pressure change. If you live somewhere higher like Denver, you're only feeling around 3000.

Small unpressurized planes, especially ultralights, will tend to fly at lower altitudes, usually within a few thousand feet from the ground. If you live at a lower elevation, this will be much less pressure change than in an airliner. If you live at a higher elevation, it would be more comparable.

That being said, it may only take a few hundred feet of elevation change for the pressure to noticeably change, and each person may react differently. If you're worried about making commitments to flight training before you know how you'll handle it, you can go on a discovery flight, even just in a small Cessna.