Q.Dropping Leaves on Peach Trees
I have a peach tree that has grown in my backyard for the last 4 years. It bears only small little peaches. Recently, it has been losing leaves off the branches. They are turning yellow, then dropping off. There are several branches that are now bare. Is this a disease or fungus? I live near Houston, TX so it is hot but we have had a lot of rain for July this year. Any suggestions would be appreciated.

Please see this article for a description of peach tree diseases.
https://www.gardeningknowhow.com/edible/fruits/peach/common-peach-diseases.htm
You didn't mention the variety of peach you are growing, but some varieties require more even more time to produce abundant crops. You might also check with your local extension office (found under gov't in the phone book) for additional help and advise on how to get the best from your tree