Are you losing too many avocados from your tree before they are ripe due to immature fruit dropping off early? An avocado tree typically can produce up to about one million flowers but will typically only set about 100 to 200 fruit per tree. Or in other words, 1 fruit in 10,000. Sometimes they will set fruit but then drop them when they are pea to walnut size. Again this is typical.
To minimize fruit drop of good, fertilized fruit, avoid stressing the tree. That is, don't under or over water the tree. There has been research in Israel which suggests that fruit retention is also facilitated when there are other avocado varieties present to provide cross-pollination and that these crossed fruit have a higher tendency to stay on the tree. We also recommend not fertilizing with nitrogen from about April through mid-June, or applying only very low amounts during this time.
Good luck and may you enjoy many avocados this year!