My 10 year old crepe myrtle has not bloomed and the bark is falling off. Is there anything wrong with this tree? Also, when and how should I trim this tree?

The botanical name of the common crape myrtle is Lagerstroemia indica. This is a genus that is going through rapid development. Many, many new cultivars are being introduced all the time. In years past, in our area, crape myrtles would sometimes grow to a large shrub, but would often not be reliably hardy during the winter months. In some winters, the top growth would be frozen back completely, but the root system will be ok, so they would basically be starting over again. Since more hardy cultivars are being introduced, crape myrtles can remain more a tree shape (like you would see in the south). On the other hand there are many new cultivars on the markert that are true dwarfs and will only reach 1-2 feet in height, and there is a great variety of mature heights in between. So keep in mind that the easiest thing to do is to match the cultivar with the mature height that you want in a particular spot in order to reduce your maintenance time and the overall effect on the plant. If you have a cultivar that wants to be 20 feet tall, this is not one that you want to continue to prune back to the ground every year to keep it short.
As a general rule, you want to prune your crape myrtle in the late spring when you start to see new growth. Cut back to new growth, or if we’ve had a particularly bad winter, you can cut it all the way to a few inches above ground and it will resprout from the root system. If you have a tree form, trim new growth from main branches to preserve the shape.
Your crapemyrtle will bloom on new wood, so expect to see flowering in later summer. Fertilize your crapemyrtle in spring-at the same time that you cut it back and again in summer when you start to see blooms.
If the blooms are particularly heavy and cause the stems to droop over, you can cut them and bring them indoors for arrangements. You might also want to remove spent blooms so that the plant will put energy into root growth instead of seed production.
You can reproduce your crapemyrtle by taking stem cuttings in the summer months. Seeds will germinate from crape myrtles pretty easily too. But keep in mind that if you have a named variety, you won’t necessarily get the same plant from the seeds. Harvest seeds and give them a cool, moist treatment for 3-0-45 days (put them in a zip lock bag with some slightly moistened peat moss in your refrigerator.) Or harvest seeds in January and sow immediately.