I would only worry about miscarriages if I have a history of them. I would try not to worry about a miscarriage unless their are symptoms leading up to a miscarriage. It is normal to feel cramping throughout pregnancy, You may feel growing pains, round ligament, sciatica nerve pain and braxton hicks. Any cramping accompanied by fever, nausea, vomiting, gush or drip of fluid coming from the vagina or period like menstrual flow should be taken into consideration asap.
Try to relax as much as you can, get at least 30 minutes of exercise..eat healthy and take your vitamins.
Make sure you write down and questions or concerns you may have for your doctor so he/she may address them at your next appointment.
I had that a lot at first to. Dr said as long as there is not a lot of blood with the cramping its normal. Your uterus is growing that's why you'll feel the cramping.