Low beta hcg?

Not sure who saw my last post but today I went to the doctor for ovarian pain and cramping and mentioned that I got a positive pregnancy test. They did one in office which was clearly positive but they told me it was negative and pushed every concern to the side like it’s normal. Well I pushed for the beta hcg test and the results were 66 mIU/mL. I’m approximately 3w5d. The doctor left me a voicemail saying this was a low number and to retest again in 2 days. Is this actually low or does this lady have me worried for nothing?