When you say that you have your doubts about something, it means that you are uncertain or skeptical about it. There are several synonyms for the phrase "have one's doubts" that can be used to convey the same meaning. These include words like questioning, mistrusting, doubting, hesitating, and disbelieving. Other possible alternatives for expressing doubt or uncertainty include being skeptical, suspicious, uncertain, hesitant, or apprehensive. Whatever word or phrase you choose to use, it's crucial to be specific and clear in your communication to avoid any misunderstandings or confusion. Ultimately, the key is to choose the word that best conveys the level of doubt or uncertainty you are feeling.