I don't know where you live, but in the US you need a pain management doctor. Be clear that you have pain you want managed and have found relief using the oxy prescribed. You should end up with a pain management doctor in goes you find a stable low dose script so you can stay functional, identify what's causing the pain, and find a better treatment method that can hopefully treat the pain vs masking it as the drugs do so that hopefully you can get through a day without pain that leaves you wishing for relief.
If you have not gotten opiates off the street that helps. If you have do your best not to mention it, but honestly it is better to be honest with your doctor. If they think you're hiding something they will likely assume it is the worst being what you fear to be viewed as.
Anyways this really isn't the place to ask this, but I just wanted to point you in the right direction of what to expect. There is nothing anyone can tell you to say to convince a doctor to give you pain meds. You know yourself and you need to present right. Either the doctor will think you are a drug seeker or patient in need and possibly due to their own bias and not your presentation. Don't get discouraged if one doctor says no and don't be afraid of a second opinion. Trust me though if it becomes a hunt I highly recommend going down this road as you do not want a doctor to provide you with a means to develop a severe dependency only to be cut off in the end leading to withdrawal hell as they refuse to ween you suggesting methadone as if it wouldn't be an even worse addiction/dependency.
Basically if you can live without opiates I highly recommend avoiding them and sticking with less severe things like cannabis, but if you do need them don't let the stigma leave you afraid to ask for help.
