seven days and counting

I figure I must be about 21 days past conception right now. My u/s is next week. Last week I was extremely busy at work and time flew by, this week is not quite as busy, and the weekend gave me time to dwell on what might happen. I try hard not to think about what if we don't see a heartbeat next week. I am terrified. Also what if we do see a heartbeat? We saw one my last pregnancy and then I lost it three days later. I want to be positive and will this pregnancy to last, but doubt begins to creep in. I have googled 21 days past conception just to see where my body and the baby should be. I don't get a lot of clear information. My boobs are tender, and I am more tired than usual. The other thing is I have leg cramps at night. What is that about? No puking yet. I am having trouble focusing on anything b/c I am thinking about the baby. I hate this, feeling of helplessness. There is nothing I can do now. I am hoping five is our number. This is our fifth pregnancy and next month will be our 5th anniversary. That's a good sign right? I pulled out the book "Coming to Term" last night and re-read the section on uterine anomalies. It did not give me reassurance. I have almost a whole shelf of books on miscarriage and infertility now. When will I get to have books about pregnancy and babies? I have to stop thinking this way. Pull yourself together girl.