Congratulations on your pregnancy. Our stories are quite similar. I also have a son, miscarried just before Christmas last year, and am now 13 weeks pregnant. I have been extremely paranoid this pregnancy and have had 3 scans before my NT scan last week (had some slight spotting). I have told my family and my in-laws but have been quite stand-offish when they ask me about my pregnancy, because I was so afraid of loosing the baby again and don't want to talk about it. I know some ladies want to talk about their losses but I'm not like that, I'd rather keep the sadness to myself. So I can understand your holding back on telling your news. It's really up to you when you feel ready to tell the family, but I'm sure they'll be thrill for you.
If you want to chat, please join our 'Pregnancy after loss' thread, everyone's friendly there and I got lots of support.
Regarding the constipation pain, yes, I had it with DS and it was really bad I took 2 days off work. SO painful. So make sure you eat plenty of fruit and drink lots of water.
All the best with your pregnancy and wishing you a boring next few months.
Me - 32
DH - 35
DS James 15/9/03
m/c 19/12/04 (8.5 weeks)