What type of redbud do you have and how tall is it? Different varieties reach different heights. How much has it grown in the past 3 years?
Generally speaking, it can take anywhere from 4-7 years for a redbud tree to bloom. The annual growth rate is said to be 12-18 inches. You said your redbud is planted in a shady spot - is that full shade or part shade? Redbud trees thrive best in a full sun to light shade location. So, hopefully your redbud is getting a little sun as redbuds will bloom more heavily when exposed to the sun. A redbud also prefers moist, well-drained soil and will not grow well in permanently wet or poorly drained soil.
For more information on growing redbud trees, please visit the following link: