Best natural drug for pain?

[f12button]

SWIM has:

Multi-Directional Instability (both shoulders)
Rheumatoid Arthritis (both shoulders)
Subscapular Bursitis (left scapula/shoulder blade)

And is looking for a natural way to alleviate chronic pain. SWIM's dad is a doctor, and yet will not give strong painkillers due to the high risk of addiction. What sucks even more for SWIM is his dad is legally allowed to perscripe medical marijuana (in plant and pill form), but would never do it. SWIM does not like taking OTC painkillers, since he kind of wants to keep the lining of his stomach intact.

SWIM is pretty much a hypocrite, since his recent actions of experimenting with nutmeg (which has not worked!) suggest otherwise.

Does anyone have any suggestions or experiences for/with a natural painkiller SWIM can take?

Thanks!