I completely understand. I had miscarriage in August last year and now I'm 19 weeks with a little girl. (: Couldn't be more excited, but still have those fears about loosing her further along (I was nine weeks when I lost my first) But it is reassuring that every time I go to an ultrasound I see something I didn't see with my first. I think writing out my feelings and talking to my fiancé about it really helped. Congratulations on your rainbow baby. Try to stay calm mama, you'll meet your little one in a few months and so will I.(:
If it helps any, a lot of women have miscarriages with their first pregnancy. I know I did, and I know a lot of women that also has. I was really scared of it happening again too, and it caused me to not be able to bond with my baby while she was inside of me in fear of losing her. Needless to say February 4th I gave birth to the healthiest baby ever lol. 12 weeks is pretty much in the clear, then even better after 14 weeks. I am sure everything will go just fine for you!
Once you're past 12 weeks its pretty clear sailing! Though there's always a small chance of something horrible happening. Just try and stay positive and take care of yourself! Congrats on your little one and hope you have a fantastic pregnancy :)