I've always had these things in the back of my throat, too, and i proceeded to find out what they were. Most people have them, or they just dont know it yet. This is something that i read off of tonsilstones.com, hope it helps, cause it helped me!: They are irregularly shaped, whitish/yellow, foul-smelling globs of mucous and bacteria that get caught in the tonsils. They form in the "tonsil crypts" which are simply small pockets or divots that appear in everyones tonsils. The scientific term for them is "tonsilloliths"...but they are more commonly called "tonsil stones". Many people have reported that their dentists have told them this is food debris, but this is NOT TRUE. Tonsil Stones don't do any physical harm, and sporadically coughing them up doesn't mean that there is anything wrong with you. However they can be annoying.(who wants to cough one up when they are kissing someone!), and sometimes they are an indication that you have bad breath. If you have ever broken open one of those white tonsilloliths, then you know that they smell absolutely terrible! What you are smelling is actually a combination of volatile sulfur compounds(Methyl Mercaptan and Hydrogen Sulfide), post nasal drip, and bacteria (no wonder it smells so bad!)
I have read and found that gargling with a strong mouth wash, such as Listerine, has helped to prevent them. When i have a cold, a stuffy nose or a post nasal drip, i tend to get them more often. So, during this time you should probably gargle more often. Otherwise, they are just a harmless bunch of little smelly annoyances that everyone has to get used to. hope this helped, bye!