pill problem

okaaaay, so I came off the pill at the beginning of November and was planning on getting the implant, after some research I decided that it wasn't for me..
my period is 2 weeks late, although I have done 3 tests and a blood test at the doctors all have been negative.
I got a prescription for the pill I used to be on, but can I start taking it again before I have my period?? you're meant to take the first pill the day your period arrives..
I don't want to start taking it and mess up my cycle even more