ive taken the precautions but still no period…?

I had unprotected sex dec. 27 which was close to when I assumed my period was going to start, but having irregular periods and skipping periods isn’t unusual, although I haven’t had once since. I took emergency contraception on the 29th and have taken two tests, both of which came back negative, including one tonight. I was under the impression that emergency contraception induced your period after a certain amount of time…the paper said if I didnt have my period within 3 weeks I’m very likely to be pregnant…tommorrow is 3 weeks exactly. If the tests are comign back negative and irregular periods are relatively normal..what are the actual chances I’m pregnant. I can’t help but be worried because at this point in my life I’m not ready for a child or a pregnancy, I’m only 16. I’m also worried because I haven’t told my partner that I’m worried I might be and I don’t know if I should or not. He’s 18 and definately not in a position to have a child either. We have continued having sex since, protected of course, and I feel guiltiy for continuing that part of the relationship without telling him. Any advice or insight is greatly appreciated…I’m merely looking for peace of mind.

ps- sorry so long:-/
if its any use last period started first weekend in december