Cramping from too much activity?

Megan

Hi ladies! - hoping a STM or someone further along can help me.

Currently at 12 weeks, and today after a short (15 minutes) walk, a (very long and exhausting) shopping trip/unpacking the car and then running after my dogs in the garden, I experienced quite crazy cramping in my lower abdomen/pelvis. It was sharp/tugging/stretching - is it just a simple case of round ligament paid or could it be something else?