Welcome to the Chronic Pain forum of Healing Well. I'm sorry to learn your fusion didn't work, but that happens for many of us.
How is the percocet prescribed? In other words, there is usually a Maximum Daily Dose (MDD) of a given medication, and with percocet that's even more important because it contains tylenol. Your doctor obviously doesn't want you taking more than 120 in a month, so that is 4/day. Also, are they 10mg percocet or 5 mg? You may be abusing your medication - and that is the case if you're not taking them as prescribed.
You really need to discuss this issue with your doctor. There are many aids now to help you quit smoking, and it sounds like you need to do that first or a doctor isn't going to do another fusion.
If you're looking to control your pain with medications only, then you will not be able to take the amount of percocet you are taking, and you need to work with a pain management specialist about other options. If you don't want the surgery, or want to quit smoking, then speak with your doctor about referral to a pain management specialist.
Still, even for those of us who have done numerous treatments and take a variety of medicaitons, they do not take away all the pain. We have to learn to manage it, to handle a certain level of pain, and to do other things such as heat/ice, physical therapy, techniquies learned from a pain psychologist, etc. and do the best we can to put an entire pain management package together. Just be sure you're taking the medication as it's prescribed, and then speak with your doctor.