During early labour, it can be difficult to judge just how quickly things are moving. Standard advice suggests you head to the hospital when your contractions are strong, last about a minute each, and have been coming every 4 – 5 minutes for an hour or two. You should time your contractions from the beginning of one to the beginning (not the end) of the next. A contraction is considered “strong” if it is nearly impossible for you to talk through it.
I hope that helps, please post any questions you might have!