Hi,I recently started using the contraceptive while on my period. The nurse told me to take the pill 7days before having unprotected sex and on the 4th day of taking the pill I had unprotected sex towards the end of my period could I be pregnant? Should I still be using the pill

You may or may not be pregnant. The pill is not 100% guaranteed to work. I got pregnant twice while on the pill.

Yes, you can still use the pill until you find out whether you are pregnant. It will not cause harm to the fetus.