I was just at the ER with my kid. Alot of kids had gastro. We were in our own room for the most part. I washed my hands alot. Will I get it?

Great hand washing . I think you did what you could considering the circumstances. Truthfully, limiting your exposure and hand washing is probably the best thing you could have done. Unfortunately, there's no way to know for sure you won't get it. Good luck!
Hard to predict. Many of these GI viruses are those you had as a kid and have some immunity to. Others are new versions and might place you at risk. The germs are in the saliva during the fever phase and the stool for much longer (weeks). Your hand washing is your best protection.