I Had A Miscarriage 2 Months Ago. I Got Pregnant

I had a miscarriage 2 months ago. I got pregnant before I had a full period. My doctor says I'm more at risk for another mc or an ectopic pregnancy. Therefore, she had been monitoring my hcg levels. At 7 weeks they were 49,000. Four days later (almost 8 wks) they did not double, only went up by 700. The doctor sounded very concerned and of course they couldn't get me in for the first ultrasound for another week! I'm so worried. Isn't it possible later in first trimester for levels to "peak" or slow down? What are your thoughts?