Hcg levels rising very slowly-IVF cycle 1

Susie

I did my HCG BETA test last Wednesday, September 13th-10 days after my ET. My HCG level was 36.8, so they told me I'm pregnant-great news! But I did another blood test today (Friday, September 15th) and my level was only 40.1, but if should have doubled by now. They were very vague with me and just said it's not a good sign but to keep taking my progesterone shots and estrogen pills and test again on Monday. It sounded like there was SOME hope, I'm just so confused at what this means and really nervous and sad.

I've tried looking this up but can't find much. I found that it could be an ectopic or blighted ovum which I don't think would make sense for someone that did <a href="https://glowing.com/glow-fertility-program">IVF</a> since the embryo was transferred. So am I probably having a miscarriage, what should I look for and is there anything I should do differently from now until my next blood test?