When it comes to expressing skepticism or uncertainty, there are plenty of synonyms for the phrase "have doubts." Depending on the context, you might say that you're unsure, undecided, or skeptical about something. Other common expressions for doubt include feeling uncertain, having reservations, or questioning the truth of something. If you're feeling hesitant about a decision or course of action, you might use the phrase "having second thoughts." Alternatively, if you're simply unsure about a fact or piece of information, you could say that you're unclear or uncertain. Whatever word or phrase you choose, expressing doubt is an important part of critical thinking and decision-making.