Im also pregnant with my second child and will be 6 weeks next week and have been havinh cramps also but didn't this early with my first baby.
I've had 5, and every pregnancy has different symptoms.
It happened to me.. not severe cramps but an annoying feeling..
I'm 6 weeks 6 days and had an ultrasound done. Everything is good and the baby is growing how it's suppose to be with a good heart beat
I know you're probably a little further along now but I had the same thing. When I was at 6 weeks I had mild PMS style cramps as my body was adjusting, stretching and pulling in both my lower and upper abdomen. And quite frequently throughout the day. I'm now 8 weeks and only feel them every now and then. Read up on it and it seems to be quite normal!
Generally with your 2nd child you'll feel more stretching pains similar to pm a cramps, due to ligaments stretching again. It's perfectly normal, but definitely see your doctor if concerned