Cramps could mean any number of things. Your uterus is growing and things are starting to move around so that will cause some discomfort. If you have period like cramps and bleeding then something could be wrong and you should call your doctor. If you haven't already scheduled a prenatal appointment you should do so. After 6 weeks your doctor should be able to detect a heartbeat with an ultrasound, or at least see something in the sac. You won't be able to hear the heart yet, but it should be beating around that time. I've had some cramps come and go but like you said they are minor. If you still have other symptoms such as sore breasts, nausea, fatigue, take that as a good sign, and go see your doctor...It never hurts to get it checked out and the peace of mind is priceless.
Im 6 weeks and have had minor cramping sinse i found out that I was pregnant
What kind of cramps are you experiencing? Perhaps implantation they dont last long.