Maybe the period was a really big implantation bleed?

This actually has just happened to my friend (who is not on IVF) They were trying, she got her period (or so she thought) and then started to get morning sickness etc. She went for a test and she was pregnant! The bleed was just some random cleaning out or else a late implantation that took some old blood out with it. Something along those lines anyway, so it does happen.

Also her bloods were very low but went shooting up after a few weeks.

So there is hope!

Hugs.