HCG levels, AF, and chemical pregnancy?

I went through my second <a href="https://glowing.com/glow-fertility-program">IUI</a> a few weeks ago. Last Friday, pretty sure AF arrived, and I had already scheduled a blood draw for pregnancy test over the weekend. Had that done on Saturday so we could begin prep for another <a href="https://glowing.com/glow-fertility-program">IUI</a>, and proceeded as though I got AF. Tuesday I got a call about low HCG level. Didn't know what that was, and was asked to come in for an additional blood draw. When I went in for the blood draw today, I talked with the nurse and she told me that HCG typically exists when there is a pregnancy. But, I thought I had gotten AF over the weekend! Did I have a miscarriage?? We did another blood draw today, and my HCG was up from 8.3 to 26. I am very confused at this moment. We are proceeding as if I am pregnant, but the HCG levels are so low that it doesn't seem like it is possible. I am going in for another blood draw on Friday to check the HCG levels, and in the meantime I am taking Prometrium and Estase.

I'm curious if anyone has heard of anything like this happening, I swear AF visited me this weekend but these HCG levels rising is making us all wonder.