No, but I did a summer of sex down in Key West.
I've not done one personally, I retreat to my garden, but I've been exposed to the concept since I was a kid. My parents did a few retreats while I was growing up and then into their later lives. A friend does them, recently returning from one and is already planning another. And one of my very favorite cousins who earlier in life was involved with the administration of Tassajara http://www.sfzc.org/tassajara/
is involved with a different retreat center these days.
I went to summer sleep away camp instead. Does that count?
If you're not used to going off on your own, as so many younger kids today were so badly helicoptered by their parents, that might be what is your overwhelming sensation. My nephew was just at orientation for going school and not having experience being away from home much, he was freaking out with some major anxiety.
For those of us who grew up spending summers away from home, it's nothing. Just ride out the weird feelings. You'll settle in fast enough and then just enjoy the experience.