are my levels low? Is there a possibility of me miscarrying again?!?!?!?

The day after my period was due (so about 2 days post conception) I had my blood drawn to verify pregnancy. My results just came back (now a week later) and the levels were at 64. Is that low for 4 wks pregnant??? I had a miscarriage back in July so I am worried sick. Also, I have three healthy children (who were also of healthy pregnancies) and with all of them I had AM sickness all the time (Cant remember what week it started though. With my previous miscarriage, I had no sickness and miscarried at 7 and 1/2 weeks. I am about 5 weeks along with this pregnancy and get a little nauseous at times, but no full blown morning sickness, as before. What do yall' think? What were your levels at 4 wks, and when did your AM sickness begin? Is it possible that I ovulate late in my cycle and concieved l8er than I think? Helllllppp?!?!?!