4 months pregnant. full intense stomach cramp (not like menstrual cramp) after lunch. lasted 5 minutes or less. should i be concerned? feels fine now.

Likely okay: The intestines, which sit on top of the uterus, are more sensitive throughout pregnancy. Food that used to be eaten without a worry, can sometimes cause pain, diarrhea, constipation etc. Stomach cramps such as the ones you describe are common in pregnancy. The hormones of pregnancy slow your foods transit time through intestine down, so more pains, naturally. If it's gone, you're likely good.