Cramps can begin as soon as implantation occurs and can go on later in the pregnancy as well. It is completely normal unless heavy bleeding occurs as a result.
Cramps can occur at anytime, pretty much from shortly after conception (implantation pains) and then throughout pregnancy. They are not normally serious unless accompanied by other symptoms...
Im 7 weeks pregnant and my cramps were so bad and severe that I was certain I was going to have a miscarriage I went to the emergency room and things were fine. Cramping can be light to severe but...