Hi Allie,
the HCG from the trigger would only be in your system for 10 days so sounds like a real BFP! congratulations.
Not sure about the IVF cycle helping you conceive but I have friends that have unexplained infertility and they have twins and a little girl from IVF and were going to do a FET with their last emby but it did not defrost so they were very upset but the month after they got pg. naturally! That is the thing with "unexplained", in theory there is nothing stopping it happening so it can happen naturally. I really hope this is it for you.