I know I'm clean, do I need to get a STD test?

No testing. If you consider yourself a practitioner of truly safe sax, if you have no symptoms and if you have no physical findings....Then no, there is no need to test.
How exactly do u kno. How do you exactly know? What special skill do you have that no one else has that you can tell you are so special not to have an std? No one can tell, just by looking or by 'feeling' that they dont have an std. Many stds are completely asymptommatic in many people. Not hvaing symptoms does not mean you are clean. If you are having sex - get tested!