How long will it take for my BFP to become darker?

morning ladies, i am just wondering is it too early for me to get worried about this...i got my first BFP on thursday, well i say BFP it was a faint one...yesterday it was darker but today i think its more or less the same as yesterday, maybe a fraction darker,...is that alright at this time too not be as strong as the control line, i am only due on today...the tests are 10ml ones.