When we are unsure about something, we often use the phrase "not rightly know". However, there are plenty of synonyms to express this uncertainty. Some common alternatives include "uncertain", "unsure", "in doubt", "ambiguous", "equivocal", "vague", "hazy", "cloudy", and "muddled". A more colloquial way to convey this same idea might be to say "I'm not quite sure", "I don't have all the details", or "I can't say for certain". By using synonyms, we can add variety to our language and better convey the nuances of our thoughts and feelings.