Ok, so last night I drank 3 O'Doul's between 10 pm- 1 am. I know that the alcohol content is very low, but it turns out I have an ETG around 8 am tomorrow morning, making my window (from last 'drink' to ETG) about 31 hours. Should I be worried at all, or am I just freaking out over nothing?

You should be OK even at that short time span due to the very small amount of alcohol... the resulting EtG should clear in the range of 13 - 20 hours. So it should be undetectable even with a 100 ng cutoff. If a 500 is used you are completely safe.

Thanks for putting my mind at ease Dr. Bill. I've also been drinking a lot of fluids today... I read some of the research on EtG's water solubility and it seems like this will help speed up the process?