Hi The sandy loam soil in this part of Texas is very acid, This bush is very invasive and hard to get rid of as it comes back from root bits. Small lobed leaves (somewhat like a wild pomegranate), 2 1/2 inch thorns, berries look like large blueberries but smooth on bottom, bark grey.
Thorn bush with blue berries
Needs a much larger pic!
Also worth cutting one of the berries open, to see if it has several small pips or a single large stone.
Resembles Ziziphus obtusifolia. However, implementing Resin's suggestions would be quite helpful.