There are 4 separate meanings of “libertarian”:
1) one who opposes authoritarianism
2) a member of a broad movement advocating reduced governmental power
3) a US political party (capitalized)
4) a pejorative used by some “progressives” to mean “anyone I disagree with”
So if you’re in that first category, which many people are, you may be correctly described under (1) while not fitting into (2) or (3). And (4) is impossible to control, but also no more meaningful than “traitor”, “infidel” or “doodyhead”. I’m certainly a member of (1); as an anarchist I’m tolerated by (2); I have generally friendly relations with (3); and (4) is meaningless because membership in it is controlled by the whims of the very silly.