I'm 4 weeks too Jess. I worry about the same thing but everything I've read says not to worry as long as the cramps aren't very painful and as long as there is only spotting or no bleeding. I hope this helps. Congratulations!
Your body is adjusting. I experienced this as well & now I'm 7 wis pregnant. I sometimes sti cramp but only like once or twice a week. Dont worry