Spotting

Habitat:

Woodland

Notes:

I see these every spring at Cane Creek Park in Cookeville, TN. It's like a ground cover off of a woodland trail. They are small plants, no more than 6 inches tall. My first guess was Periwinkle or Greater Periwinkle, but Blue Phlox is also very similar. What is the difference in these flowers? Which one is this or is it something else?