open the bonnet and look closely at the A/C cylinder. There must be a glass on top of it and if you can find some bubbles in it, then its problem of Gas.
But as your above described conditions shows more probabilities with compressor. normally its not repaired. If someone will do, then it will start malfunctioning very soon.
better take your car to Punjab Car A/C or CoolSun. Both are nearly Ganga Ram hospital.
Specially Punjab Car A/C is expensive, but they guide more correctly.
Punjab Car A/C installed denso AC in my old car. At that time he charged me Rs. 10K extra than other car A/C dealers. And he told me about it very clearly.
And good thing was that after installing that A/C, i ran the car upto 7 years and not even once the AC was serviced. And when i sold it, its AC was working as good like new.