There are definitely women who do get pregnant with progesterone levels close to 5 roughly a week after ovulation, but most of those women will be put on progesterone supplements, and if you routinely have "weak" ovulations, a doctor might consider Clomid or Femara to raise your progesterone levels. I'm not sure where CD26/27 falls for you in terms of days past ovulation (assuming no luteal phase defect, I know it should be ~day 16, but there's no way to know that for sure without some form of self or doctor's monitoring). Are you temping or anything? You definitely *could* have ovulated, but 5.12 would still be considered low progesterone at 10dpo. From doing a lot of searching online and what my OB/GYN says, on an unmedicated cycle (no Femara/Clomid/injectibles), over 3.5 on 7dpo means you "possibly" ovulated, and anything over 5 means you ovulated, but many doctors will say to indicate "strong" ovulation that would better sustain a pregnancy they want to see a 10+ on an unmedicated cycle and a 15+ on a medicated cycle. I've heard that soy iso -sometimes- can cause anovulatory cycles, especially if taken every day or in high doses, but without trying a cycle without it and comparing progesterone levels, there isn't a way to say for sure what it did this time around.
Sorry I couldn't be more definite; I hope some of that helps, at least!
