What kind of cramps are normal during pregnancy?

During my research I have found several women (including some of my close friends) who have said they also had horrible cramps during their first trimester however it has yet to calm my new motherly worries. I am a young mother at twenty and have experienced cramps worse than period cramps and I am six weeks long. At first I thought this was because just over a week ago I should have had my period but now that time has passed and they are still occuring. Luckily, I have not had any bleeding but first miscarriages are all too common in my family (both grandmothers, mother, as well as aunts). I know no one can tell me a miscarriage will not happen, no one knows, but if someone could ease my distress about this syptom I would greatly appreciate it.