right where the top of my sons head is, is cramping so hard right now :( kind of like when they…

right where the top of my sons head is, is cramping so hard right now :( kind of like when they check to see where my uterus starts above my pelivic bone, but this cramp lasts longer. I'm so uncomfortable, had a horrible night with my sons father, and completely stressed that I'm 33 weeks pregnant :/