Thanks for your query.
At 37 weeks and with 3 cm dilatation and 75 % effacement, you should not be taking these pains lightly.
Specially, if you have had 2 children before born vaginally, it is likely that the third time, labour might be speeded up.
Labour pains start from the lower abdomen, but radiate to the back and hips also.
Associated with that, you might perceive intermittent hardening of the uterus
Also, slight vaginal discharge
Please visit the hospital for check up