Emski: Don't panic Luv!!! I had exactly the same thing happen to me when I got my BFP too. It was a withdrawal bleed Luv as it happened exactly when my period was due. It was bright pink as well and only happened when I wiped..a very small amount that never really went beyond that. Just a few spots on my "Feminine Hygiene Product" when I checked the following morning and fully expected to see AF had arrived, but there was Nada!!
Your HPT's are getting darker which indicates you are Preggo with a true BFP girl!! If it was a Chemical, the line would of disappeared by now based on the pic you posted on your blog (which clearly shows a line there). Mine got darker too btw No, I truly believe you've just experienced a withdrawal bleed and nothing more. Nevertheless, feet up as much as you can, your body is still out of whack from the flight and is "resetting" itself, so speak.
Everything will be ok Luv The time to panic is if cramps kick in big time and bleeding starts up in earnest and is dark red etc...you know, the usual sh*t when AF makes an unwelcome appearance which I'm confident she won't!!
Am here right behind you Luv, watching and waiting and stalking!!! Keep resting and keep on POAS as well until you get to BT which is Monday??? I'm pretty sure by then you'll see a line that's off the charts!!
Breathe my darling and believe.....