No. Reserved means being quiet and unassuming. Secretive means furtively doing something, while not wanting others to know.
Reserved is a personality trait (yes, it can be more permanent). Secretive is an occasional state of mind or necessary mood.
By the way, your instincts are telling you something good. Those who feel or have inklings of the subtle differences in meaning are close to mastering, or at least grasping the language as a whole, and appreciating it as an art of communications and expression.
--lotus