First I agree with the previous posts that stated RU and OP are two different chemistries.

Second, if your doctor won't/can't get you to a specialist, change doctors!  Or,,,, at minimum go to someone else for a second opinion, even if it means going to OK City, or Dallas or Houston.

Lastly, something to ponder..... Years ago a local farmer about died from exposure to Methyl Parathion.   He had spilled it on his leather work boots early in the year, and they were giving him a slow release dose of it for weeks (maybe months).  Then,,,,, when he sprayed some again he got REAL sick from the 'double exposure'.  Any chance you're picking up some chemical from clothing, home furnishings, car, truck, tractor interior, drinking/bath water????