Yeast/Thrush

Ok so my LO had antibiotics almost 2 months ago. We fought a diaper rash from the nasty poops. At her 6 month check up I showed the pediatrician. He said it wasn't yeast yet but would turn into yeast if not treated. He prescribed her nistantin cream. The rash went away and came back about a week later after being at the beach/pool for several days. She's on a new treatment. I'm just curious...does yeast diaper rash mean she could have thrush? She has no symptoms of thrush and neither do I. I'm so nervous about getting thrush!