My husband and I have been trying to conceive for a few months. This time round we felt we hit the right dates for Ovulation, and started getting pregnancy symptoms such as Acne, and extreme tiredness. Also, 2 days before my period was due I started cramping - and normally I never cramp before my period.

My bleeding then came one day after I would expect AF, and was much lighter than usual, but lasted the same length of time, and my BBT stayed above the coverline during the AF, while usually it falls below the first day my period arrives.

Right after AF, my BBT went down below the coverline, yet I took a pregnancy test anyway, which was negative. So I now have low BBT and negative pregnancy test, but I still have acne, which I don't usually have, my breasts feel firmer / heavier and slightly larger, and I'm still extremely fatigued, and my hair loss has increased noticeably!

Am I imagining things or should I suspect pregnancy? How can I be pregnant with low BBT and no BFP 3 weeks after Ovulation?

Has anyone heard of anything like this? Should I see a doctor?

Thanks everyone in advance for your help.

I'd wait until your period is due next month and see what happens. Usually your temp will stay up if you are pregnant, but if you haven't been temping and charting for awhile, it may just be an error or a clear pattern hasn't been seen yet.
The symptoms you had may have been from your period... even if you don't normally have them... hormones fluctuate, symptoms can change.
It does sometimes happen that a positive result doesn't show up for several weeks... all you can really do is wait and see what happens.