I just had my third foot surgery and in quite a lot of pain. i heard that people develop immunity to the painkillers. is there any truth to this?

No: People can experience tachyphylaxis to medication or the medication stops working. If you are having pain that is uncontrolled by your medication your doctor needs to know. Foot surgery is quite painful.

Pain killers. : I would not call it immunity. I would call it a tolerance. So the more pain medication you take your body builds a tolerance over time. This may require you to take more medication at a different dosage or change medications. Also pain can fluctuate based on the type of surgery performed.

Surgery: Foot surgery can be painful , but doesn't have to be. If you are having pain not covered by your medication call your surgeon asap- it could be more than just the surgery that is hurting such as a tight bandage.

Yes: People often develop tolerance to pain killers when used chronically. In fact, a drug holiday is often used in order to recover from the pain. However this should not be a problem when the pain killer is used on a short-term basis.