Tonsiloliths have a variety of causes as you've already read. They can come and go. I found that mine were caused by smoking, post-nasal drip, and not brushing my teeth/tongue enough when I wasn't taking good care of myself. You don't have sinus problems or stuffiness, but it could still be post-nasal drip. They're basically a collection of mucous, dead skin cells, and food plaque and bacteria which cause the characteristic bad breath smell.

Anyway, brush twice a day, including your tongue right to the back. Gargle with peroxide and water or salt water twice a day. Another thing you can use to remove them, aside from a wet q-tip as mentioned earlier, is a measuring syringe, the kind you would use for dosing children's liquid medicine. You can ask for these at the pharmacy, or ask your dentist for one. Dental irrigation syringes work better because they have a curved end to fit into crevices better. Fill it with warm water, poke it GENTLY into the opening in your tonsil, and squirt the water into your tonsil. This should dislodge it. Keep a glass of water handy to immediately gargle and spit. You'll see the tonsiloliths in the sink. They are white/yellow/greenish, odd shapes and sizes, and smell bad. Your throat might get a bit sore afterward.

Have fun!