Need help. Neutered cat. Infection

[Abraham1]

On Wednesday I neutered my 10 months old cat. Every thing was fine that evening Thursday evening my cats health started to get bad. He stopped eating and drinking and the sac got swollen and on one side of it it was turning red now purple like pictures. I took him Saturday 2 am gave him a shot of antibiotics and he got fever too. Then he ate a bit every now and then. Some ooze came out during the night of Sunday too. He is still on antibiotics but very worried his fever went down a bit but still a bit high. I don't wanna lose him he's our only child. Anything else I can do? I am very very worried