Stomach pain

Im 24 weeks and 4 days. My stoamch has been hurting for about an hour. It hurts down low and up the sides. Its a constant pain. It also feel heavy or tight and I feel like I have to poop but nothing is coming out? Should I be concerned or is this just a stomach ache? This is baby number 2 but u never went into labor on my own so I dont know what yo expect really.