Confused..

I’ve been on the pill for 3 weeks. My fourth week began Thursday (the week my period is meant to come).. my period hasn’t come yet, I forgot to take the pill about two weeks ago (only once but I took it within 12.5 hours after.. I take it at 9pm.. didn’t take it till 9:30am) me and my boyfriend had sex and the condom ripped.. we had unprotected sex but pulled out.. I took a pregnancy test Friday and it came back that I wasn’t pregnant, could tests be wrong or is it possible to miss your period when you first get the pill?? Please help..