4 weeks 6 days pregnant but HCG levels seem low


Help! I need some advice!! I found out on Sunday I was pregnant! First i was shocked but then excited. Hubby and I have been trying for about 6mos for baby number 2. I went for bloodwork Tuesday. HCG level was 28 I/uL. Doc office was concerned it was too low so I went again Thursday (yesterday) and HCG was 51 i/uL. They are concerned my HCG levels are too low. I had a very small amount of dark red spotting nothing else. I’ve been crying on and off all day. We are so excited for this. I would be due Feb 9 2020. Anyone else have low HCG levels in the beginning?? I have already had one miscarriage and don’t think I could go through another one.