Noooo, not at all. A woman who has sex with a serious boyfriend she loves and with nobody else ever would not be labeled a slut by many people, except perhaps batshit fundamentalist Christians. Also, someone who never even has sex but fools around with lots of people can be labeled a slut.
And also, it’s the case that having sex out of wedlock and having sex “without emotion” (what the hell does that even mean? doesn’t describe anyone I know) makes people uncomfortable, which is WHY they feel the need to demean people (read: women) with that word.