Teepee there was a young IVFer a couple of years ago who had a HCG reading in the 20s at her 14dpo BT. Her Dr said it was not a viable pg. She, however, continued to confound them by having her HCG increase a little with each BT. They kept telling her it was not viable, it might be an ectopic etc until she had her first scan. She later went on to have a healthy, happy son.

With OI, it's so hard to pinpoint exactly when fertilisation took place, or even when implantation might have happened. The best indication will be your next BT. Good luck.

BTW it's true that my HCG was 75 at my BT, as BW said. That was when I was pg to Charlie. At that time, there were a few of us LTers who had low HCGs. We all went on to be belly buddies and baby buddies together.