Would my HCG levels rise this high if I had miscarried?

I went to the doctor for a transvaginal ultrsound when I experienced mild spotting (this occurred right after intercourse and there has been no spotting since). Going off my LMP, the doctor assumed I was around 7 weeks pregnanct despite the fact that I don't think I was more than 4-5 weeks into my pregnancy. My HCG beta level was at 19,000. The doctor was worried because he could not detect a fetal pole or heartbeat. A subsequent HCG test two days later revealed my levels had risen to 31,000. There were no molar "growths" observed, and I have another ultrasound scheduled for tomorrow (this marks a week since the first u/s). I still feel every symptom I felt before this doctor's visit but am very worried since he indicated this might not be a viable pregnancy. Would my HCG levels still continue to rise this dramatically if I had miscarried? I am 33 and this is my first pregnancy. Any advice would be appreciated.