Is labour close I am overdue?

Hi I'm 40 weeks pregnant and it's 3 am I am in agony... I have the most horrible dull ache at the bottom of my back that I just can't sit easy wit... The only thing is it's not getting worse and easing off like contractions it does feel like a period pain an like I need the loo but can't... Is this things startin off or should I just try t sleep