You mention high tolerance to "narcotics" - I'm guessing this means opioids. (Unfortunately, the pejorative application of this term to include all psychoactive substances that get used recreationally has muddied the original, specific meaning.) Anyhow, it sounds to me as though you may also be a strong metaboliser, especially if you noticed this tolerance before ever having any SSRI,etc., treatment. Some medications also upregulate metabolic clearance, I'd have to check specifically for the ones that you've listed. The upshot is that you may well be deactivating DMT through the CYP2D6 'side route' as well as having downregulation of the serotonin pathway both by competitive receptor blockade and glutamate suppression.

This is my series of educated guesses, at least!