Dog hasnt pooped since surgery-should i be worried?

Sounds like your dog hasn't been eating much so her intestines are empty. This in most cases is normal The fact that she's farting indicates that her digestive system is beginning to work again. Call your vet for sure if she seems to be uncomfortable or starts straining to defecate. You should give your vet a call anyways and give him an update on your dog's condition. This is where you can discuss this problem in more detail.