Super late period and negative pregnancy test!

Hey ladies. My period is almost 2 weeks late ( it has never been super punctual, but never more than 4-5 days). I've been having sex with my boyfriend and we are using withdrawal method, he has never came inside. Just to be sure, i did a pregnancy test and it was negative but I'm still not having my period. Have any of you experienced something similar? Any advice or suggestions you could give? I'm really starting to feel desperate...