Thank you!! Yes I was tested at 4 weeks so it's anyone's guess when I ovulated..:)
I had low HCG levels at first as well. You may just not be as far as you thought. My ovulation has been off so by going off my last period, my HCG would be at 500+ but it was only at 14. Come to find out I had ovulated over 2 weeks late and was only just implanting. They do the test to make sure your numbers are close to doubling as they should, this can validate your healthy pregnancy.
Mine started at 14 then when to 72 in 2 days so we knew it was good. After my 6 weeks sonogram it was obvious I was only 6 weeks and not the 9 they assumed going off of my last period. We had assumed as much since the HCGs were low.
Good luck. Increase your caloric intake a bit and progesterone increasing foods and decrease estrogenic foods for now.