When you're not sure about something, you can use synonyms for "have one doubts" to describe your uncertainties. You can say that you're apprehensive, hesitant, uncertain, or skeptical. If you want to express your lack of confidence, you can use the words dubious, mistrustful, or suspicious. You might also say that you're unclear, unsure, or indecisive about something. If you need more conviction to make a decision, you can use the words skeptical, skeptical, or incredulous. By using synonyms, you can better communicate your level of confidence or uncertainty to others.