Walking and cramping?

I'll be 20w tomorrow.. I park about a half mile away from my work and walk to and from my car. Walking to my car tonight I started getting cramps in my lower stomach/pelvis. I wasn't doubled over in pain, but definitely uncomfortable. I feel better now, just aware that the cramping was there. No bleeding or anything associated with it, should I be worried? Is it possible I overdid it? (I know that sounds pathetic)