tripac issue

Either you have a blower or ducting problem, or your evaporator is freezing up blocking air flow.

The blower motor could be bad, but that normally happens suddenly instead of gradually getting worse and worse. And the ducting could have come apart or be blocked, or the air filter could be really clogged up.

Evaporator freezing is normally caused by low freon, but could also be caused by a clogged or stuck expansion valve (or orifice in some units). If it blows air fine each time when first started, then gradually loses air flow, I would check the evaporator first, to see if it's freezing up. It's right behind the air intake filter under the bunk, and should be visible if you take the top cover off. If it's freezing up bad enough to block the air flow, it should be obvious.

And you can see if the blower motor is working while that cover is off.