Hello. I can certainly understand why you're concerned about this issue. Taking multiple i-pills within the space of several weeks will very likely disrupt your menstrual cycles and lead to spotting, irregular bleeding, and/or skipped, early or late periods. Since your pregnancy
tests have all been negative -- the latest being 16 days after your expected period -- it's very unlikely that you're pregnant. Your periods are undoubtedly delayed due to your repeated use of the i-pill.
Since emergency contraception
is less effective than oral contraceptives and more likely to disrupt your menstrual cycles, I suggest you see your doctor to discuss getting on birth control pills. In the meantime, use condoms every time you have sex.
I hope that helps!