Ay, cramping at week 6 is quite normal actually, a few of us went through it and it scared us half to death! But honestly, you should still check with your doctor or midwife to put your mind at ease, especially if the pain is really bad or you're bleeding, sebab they need to rule out anything else. Sometimes it's just your uterus stretching and adjusting, but better safe than sorry lah when you're pregnant.