It's been plaguing my mind for the last 5 years or so. And I don't know what to do or think about it...

Firstly, not actually sure if it's related but I rarely ever get sick but my overall conundrum is that pharmaceutical drugs rarely if not at all have an effect on me. I have tried and have been given doses that would severely impair or kill most people. This includes variations of diazepines, opiates, muscle relaxers, THC, amphetamines, alcohol and even Including local anaesthesia....and I'm NOT even an avid drug user....Doctors have told me they don't understand it and I can't find anything in regards to research. All I could really find is that a large population of the British are immune or fairly tolerant to weaker forms of opiates....Does anyone else have this condition? Is it fairly common? Is something wrong with me? I'm so lost....