Half of my holly tree has leaves, half of it doesn't! Also, there are no berries. Last Christmas the tree was fine and had berries! I did cut some limbs off to use for decoration. However, not but about 3 or 4. Maybe it needs to be fertilized?
It sounds like your holly has some kind of disease, or possibly an insect infestation. This article will give you an idea of what to look for: https://www.gardeningknowhow.com/ornamental/shrubs/holly/diseases-of-holly-bushes-pests-and-diseases-damaging-holly-bushes.htm.
Cut off the damaged parts, and try to get an analysis of the leaves and branches. You can get this from the county extension service, if you're in the US. This link will help you find the nearest office:
In the Uk, you can seek out the Master Gardeners http://mastergardeners.org.uk/get-involved/find-your-nearest-master-gardener/
or call any nearby botanical garden for assistance.