Is it normal to not have any after-sex smell? i never experienced absolute no smell after sex but w/ new boyfriend theres none. what causes no smell?

Seems a good thing: Having a smell means having an undesirable odor, to most people. Thus, in our modern world emphasizing cleanliness, the lack of a smell is a good thing. We worry more if there is an unusual or undesirable smell. Nice aromas are nice. Other odors are probably best if they aren't noticeable. Odors are generally due to combinations of one's oils, bacteria, yeast, bodily chemicals, etc...