If you have an Echo, or another Alexa device, it could be listening to your conversations if your wake word is something you use often. Amazon claims that only relevant conversations are stored, but if you want to limit the amount of conversations that fall in this category, you may need to be more cautious. Change your wake word to something that you rarely use so that your private conversations are not recorded. Remember, even words that sound close enough to your wake word can sometimes turn on the device. See our how to protect your smart home article for additional info.