I agree with the above post. Take it easy and treat this pregnancy like a new one. It's hard not to compare especially when you feel like you'll be preparing emotionally but actually you could be stressing for no reason. I had to talk myself off the paranoia ledge constantly because I too miscarried. I also have a great support system. Now I'm 16 weeks and happily pregnant.
Some menstrual like cramps and back pain are typically normal at 7 weeks. I have had 2 miscarriages and I know the fear you are going through. The best advice I can give you is, take it easy as much as possible. If you are concerned about a possible miscarriage call your doctor, she/he will be able to help you more.