Mild/light cramping?

Sandy

I'm 23w (tomorrow) and since Saturday (I did a 10km walk...used to be more athletic but not so much this pregnancy) I've felt on and off very mild cramping. First day I assumed growing uterus and perhaps I overdid the exercise/walking. But felt it again yesterday afternoon and now that I'm waking up and starting to walk again I feel mild discomfort. Is this normal at 23weeks? (FTM here)