No, I didn't swear.
SWEARING, properly defined, is when you enter into a sort of contract giving God the right to do something very bad to you if you're lying or you fail to keep your word. If I say
"Well, I'll be damned"
or
"You come down from there this minute or so help me God I'll come up there and kick your ass"
I'm swearing, though I may not be consciously aware that I am. The resulting speech act is properly termed an OATH.
Then there's CURSING. As the name implies, it involves expressing a wish for bad things to happen to something or somebody. If I say
"Damn this hot, muggy weather"
or
"Go to hell"
I'm obviously cursing.
Both swearing and cursing, when they're used not in spiritual earnest but simply as a secularized expression of the intensity of one's feeling, constitute PROFANITY--that is, language that takes sacred things and uses them in an irreligious context. Profanity can include other forms of language that don't necessarily fall into the categories of oaths and curses, though. If I say
"Jesus H. Christ--who the hell do you think you are?"
I'm engaged in profanity. Profanity has lost a lot of its force in the last hundred and fifty years, as society has become secularized. So a lot of people have turned to OBSCENITY to take up the expressive slack--which properly refers to the "dirty" language of bodily functions when such language is used primarily in order to shock, to offend, to titillate, etc. I try to avoid using earthy language for these purposes in my everyday life--not because the words themselves are wrong, but because A.) it's not nice to want to offend people, and B.) [as a character in one of Vonnegut's novels points out] foul language gives people around you free license to get angry and offended and not actually to engage with whatever you have to say.
For instance, if you yell at your roommate to
"Pick up your shit!"
when what you really mean by "shit" is "dirty socks, empty Coke bottle, and last April's issue of Maxim,"
you're using obscenity, and your roommate will quite likely respond with hostility and defensiveness--and with more obscenity.
But if, in discussing the problems of disposal of human waste in an outdoors/recreational setting, I use the honorably Anglo-Saxon word "shit" to refer to said human waste, have I used obscenity? I don't think so, any more than a women's-health website is being obscene when it talks about "breasts" in the context of mammograms and self-exams.