If you were 4 cm dilated and had strong sharp lightening crotch, would you go in to L&D?

If you were 4 cm dilated last week and now you're having strong sharp lightening crotch, would you go in to L&D just in case? I'm having menstrual cramps also and pressure. But I'm just curious for those who have gone in to labor. When do you know that it's time to go?