Fido's like a little girl haha

he cries out of something that is nothing, If i step on his coat he screams also! even if he doesnt hurt a bit

if he's uncomftorble he screams.
Fido wheighs 6 kilo's , i think its about 15-16 lbs, he's very big.
Right now he's 6,5 kilos, he was 7,5 kilosthis summer cause I changed his food and it made him get really really fat! when he's in the right wheigh he's about 5,5 -6 kilos, something under 6 kilos propably.
The surgery here costs about 1 thousand and 500 dollars, its EXPENSIVE ! but if this gets worse and he's often in pain (Fido is never in pain i think) then ofcourse I will get him into surgery, its just also long recovery time and the surgery would be so hard for him, I dont want to do it if I dont have to.
Fido is 2 and a half years old

He was born 13 July 2008.
My vet reccomanded me that I keep him in a good shape, exercise him well, so he gets much muscle around the knee.
Do you think that is wrong ??? they are very good vetnarians that I know personally, I work at their clinic.
Fido does not jump much, hardly anything, he just jumps in my bed and sometimes in the sofa (not often).