I obsess over saying the wrong thing

Okay. I have a problem. Sometimes, while in conversation, I might say something stupid or something that I fear has offended the other person in some type of way. For example; today I was talking to my boyfriend and I said something incredibly stupid, or atleast I think so. See, he has my phone...and I had told my friend Casey on FB to text me her number. So if she were to text me, he would receive that text message. His ex girlfriend from a couple years ago was named Casey, not the same Casey, of course. But, anyways, I told him that if he got a text message from a girl named Casey, it was my friend Casey, not his exgirlfriend Casey...Now, ever since I said it, I've been obsessing over why I am so stupid to say such a thing!?