it's quite possible you caught a disease of some sort if every person is saying it. I only get one person in the Alchemy shop in White Run who says it to me even when i've caught nothing. When i have caught something, thats when other people start saying it. In Skyrim, you get more diseases unlike Oblivion, you can catch them from attack, maybe lack of sleep or other things. Go on to your inventory where you get the skills, equipment, map and magic. Go on to Magic and somewhere at the bottom, i believe its under Shouts, it will give you a list of constant effects be it enchantments, gifts from the gods or diseases. I can't remember the actual name of the list you have to go on, but it's under magic. If you have caught something, the name of that infection will be coloured in red. The best thing about Skyrim when you caught something is that people actually hint out to you that you look ill. I didn't understand it at first until i discovered i had caught a few things. Not to mention if you did catch something, the red indicates its effecting you in a bad way. The best way to cure it is through the shrines you get in every city. I don't actually know if there are shrines in every city, but it's best to go there than run around looking for a Shrine out in the middle of nowhere. I always go to White Run to cure myself, the building is next to the tree in the middle of the city, i do believe the building is called Temple of ?????, just go to the end of the building and you will see a little shrine, click on it and it will cure you're infections. I do not know if being bad will stop you from being cured though.