Important to note "having a fast metabolism" in regards to weight management does not carry over to your body's reaction to consuming drugs. Keif' Richards is on the right track. The subject matter deals with Pharmacogenetics. This has to do with mutations and expressions of certain of alleles present in the form of liver enzymes (p450). Are you an ultra rapid metabolizer, complete, incomplete, etc? There are cheek swap test available for this and is has a profound clinical importance for Pain Mgmt and Psychiatry. Of course you can't march straight to the doc and ask for one, you'll need to prove necessity. Maybe you are an ultra rapid metabolizer. This plus the fact of time release would mean your oxycodone plasma concentrations are very low and thus little dopamine release (euphoria/high). Just a suggestion.
The other half of it has been covered... you really don't know what to expect at first. I didn't. It produced lethargy, nausea, sedation. It wasn't until a few sessions did I realize what I found. It's up to you to keep trying, but it will leave an indelible mark. I wouldn't recommend smoking a bowl as that may make it more difficult to find what you are looking for.