Really worried about miscarrying? is this normal?

All the women in my family have had history of miscarrying. My mom had 2 and she's been telling me my entire pregnancy not to get my hopes up because there's a high chance of miscarrying. She said she'll get mad if I announce my pregnancy before 12 weeks. I've always had horrible, horrible period cramps and was worried I had a fertility problem but I got pregnant before I needed to find out. I'm 7 weeks now and I'll get really bad cramps in my uterus every second day or so. I saw the heartbeat flickering away last week at 6 weeks and 3 days and she said everything looks great but I'm still so worried. I'm also dealing with the stress of a loved ones death and some negative people in my life and I'm worried that may be hurting the baby too. Has anyone else been so worried about this, and do you think all sounds okay? I'm so scared to lose this baby. He or she is my life. I haven't bled or anything but I've heard stories of people going in for ultrasounds and finding out their baby's wart stopped weeks prior and that's what I'm worried about. Please help. I'm driving myself insane. :(