It sounds like your compressor is working properly. It sounds like your expansion valve is o.k. Your receiver/dryer could be saturated. That is your A/C filter, it has desicant in it to suck the moisture out of the system. Your best bet would be to bring the car to the shop so they could put the recycling machine on it. They could check you high side and low side presures, and make sure it is cycling properly. They would run it into a vacuum to make sure you don't have any leaks. Also they could run your R134A through the recycling machine and take out all the impuriteis in the system. They would also make sure you have enough oil in the system.
If you have never had your A/C serviced and putting a shot of R134A did not help and the compressor is cycling properly, I would put money on the receiver/dryer being no good. There may be a small sight glass on the receiver/dryer blue is good red is saturated.
