What Causes Mild Persistent Abdominal Pain?

I have some pain in my abdomen it s been hurting all day but not badly and it especially hurts when I walk but I can feel it sitting and laying down too. I don t have a fever and I m not throwing up although I feel like I want to even though I m not especially nauseous. It also hurts a bit when I press on my stomach. I m not sure if I should go to the ER since it isn t a sharp pain or if it might be something more serious. The pain is more towards the top of my abdomen ranging towards the middle on both sides. I m also on my period but this doesn t feelclike cramps.