Thanks for writing. This is actually one of the most common questions we get --- so don't feel bad.
In your area, one of the typical issues is improper pruning. Many hydrangeas make their flowers the year before they bloom --- so if you cut yours back in fall, winter, or spring, you're probably cutting the buds off before they have a chance to grow.
If you don't prune yours back, then it may be an issue with your growing conditions. If they're in a spot that's too shady they won't bloom well. Likewise, if they're in rich soil and you fertilize them (or they're next to a lawn that you fertilize), the extra nutrients might be going to leafy growth at the expense of blooms.
Because they make their blooms a year ahead of time, they're susceptible to getting zapped by a late-spring frost.
Learn more here: http://www.bhg.com/gardening/trees-shrubs-vines/shrubs/why-wont-it-bloom/ "