Dry heaving after concert.

So I just got back from a concert which lasted about 3 and a half hours, at the end of it I was dry heaving when I walked out into the car part. What's going on here? I had a lovely time at the concert and I get the massive sensory overload with just 5 minutes of relief when I went to the toilet, but this is the first time I have reacted like that. 

Thanks.