See if there is a pattern to the cramping. And time them. It may be contractions but if there isn't a pattern then it probably isn't true labor. If you are too worried call your nurse line or doctor.
You can always call your doctor for some questions but, here are some infos to help.
False Labor signs:
contractions are...
-irregular and unpredictable
-confined at lower abdomen and groin
-disappear during ambulation & sleep
-no progressive increase in duration, frequency or intensity
True Labor signs:
contractions are..
-irregular then becomes regular and predictable
-pain starts at lower back and sweeps around abdomen
-pain continues on ambulation at any level of activity
-progressive duration, frequency, and intensity