braxton hicks

I was walking to a book reading tonight. All of a sudden my belly felt like it was going to burst/pop. The sensation made it difficult for me to walk. A friend of mine told me those are Braxton Hicks. Since I've never felt them before I didn't know that's how they felt. I guess I've been having them since about 30 weeks when we were on Martha's Vineyard. I felt these tightening sensation in my belly/uterus. I think 30 weeks might be a little early for practice contractions, but then I read on pregnancy-info.net that you can have it anytime in the beginning of the first trimester. I guess maybe it's not too early to have them at 30weeks. We were walking around a lot and probably dehydrated, so that may have caused it. I am fine now of course, but we had to sit at Oaks Bluff in Martha's Vineyard for about 1 hr since my belly felt like it was about to burst.