Could this be early signs of labor?

I have abdominal cramps now and then, sometimes even shooting/stabbing pains. My legs and feet and lower back are generally sore if I've been particularly active. So to me, these don't sounds like signs of preterm labor. But, it never hurts to get a doctor's opinion, especially if it's your first baby. Call your doctor's office, even use the after hours number, just to be sure.