Greetings,
I would hypothesize that you took on these people's energies and your body naturally purged when it was able.
It is very common for the inexperienced to do this, especially when you so want to help. I've had the same experience a few times and it scared me out of my wits :-), with me questioning Reiki quite a bit afterwards. But I've since learn't that it wasn't the Reiki per se, it was more of a natural tendancy that I have (ie. taking on other people's stuff) and being so wide open I had no 'defence'. If it happens to me now, I simply reconnect with my guides, they take over and I recover physically.
Hope you figure it out.
Peace
Nats
