There's a lot of different hybrids or cultivars, whatever they are, of Mock Orange. They all don't have the same flower. Most have a really sweet smell, some don't. The one thing both plants that have been suggested as possibilities for yours have, is that the flowers have a fragrance. Unless you happen to have one of the mock oranges that have no smell! Now that would seem odd to plant something like that. Plant something known for it's smell, but plant one that has no smell.
Chionanthus virginicus is native up to NJ, down to FL and all the way over to TX. Not just in the SE. If it is this, it needs a mate. It berries with a mate. Unless you have more than one??