the difference between Braxton Hicks and the real thing?

I know that BH's aren't meant to be regular but I'm getting regular period like pain, every 2-3 mins at the moment and I'm only 34ish weeks along. Is this something I should be worrying about? Bubs is already engaged and I've been nesting a lot lately... I haven't had a show or broken waters but should BH's be regular like this? They have been regular for over half an hour and haven't stopped when I walked around or changed position.