Claire, if your period lasted only 1 day, I'd wait a bit before trying anything. If it doesn't come back, do another HPT in a couple of days and/or see the GP. There are women who have had what appears to be AF even whilst pregnant - you really don't want to start taking anything if there's still a chance.
I was visiting my parents over the weekend, then stayed an extra night. We'd moved the visit from this coming weekend when we realised the likely ov dates - then I started panicking that I was going to ov really early, when I had EWCM from CD9! Absolutely no chance of BDing there - paper-thin walls and I'd have to walk past my parents' door to get to the bathroom afterwards

And we all know what the 'walk of shame' is like, clutching a handful of tissues and hoping you make the loo on time!
My father spotted my CBEFM sticking out my washbag and asked what it was.

What would you have said? I muttered 'women's stuff' and DH said 'I think it's some kind of hair removal gadget'!

I'm not sure that was any better than the truth, actually, but I was impressed by his quick thinking!