Slow labour?

I'm hoping someone can help - I'm 37 +2 pregnant with my first child, and have had a horribly painful period like contraction at 8.30am this morning. But I've had nothing else at all? I've had braxton hicks but this was nothing like that - it was unbearable pain! Also "down there" is aching a lot and I'm having to use the toilet a lot (number 2) can anyone help? Am I in slow labour?!