Could be a gnat or a fruit fly. Many insects see in the ultraviolet part of the spectrum. Carbon dioxide reflects UV light, and the bug may be attracted to the sight of your breath. There's no much you can do about it - other than to stop breathing.

You don't give much of a description of the bug so I can only guess what kind of bug it is.

pls help thur is this small tiny black flying bug everywhere in my house and it wont go away!!!111 they always fly everywhere and sometimes that annoying little black flying bug comes up to my face (no buzzing noise) (pls name it for me also)