Low HCG

Hi,

My last AF started on July 31st. I got 7 positive home pregnancy tests on 9/7, went to urgent care the next day and got a negative urine and a positive blood test at a HCG level of 53.4. On 9/13 I had an annual appt set up at my OB and I told him about my positive pregnancy tests. He drew a quantitative HCG and it came back at 84. Based on my LMP I should be about 6 weeks. I'm notoriously irregular with my cycles, so could it be possible that I ovulated late to explain low HCG levels? I've had no cramping or bleeding, and no pain in general. I've had symptoms of very sore breasts and nausea here and there, with lots of fatigue, so I definitely FEEL pregnant. I took another HPT tonight and the digital still says pregnant. Anybody have input?