Thanks for writing in.
It is unlikely that you are pregnant. Irregular menstrual cycles are commonly seen in anovulation
( a condition where no ovulation takes place). If there is anovulation, you cannot conceive. Further since the tests are negative and are about 95% accurate, it is unlikely that you have conceived.
Please stop taking pills without the supervision of your doctor. These can be dangerous and can lead to fatal amounts of bleeding. In all probability, you would get your period within 1 week.
To be doubly sure, you can get a beta hCG
level done in your blood to definitively rule out pregnancy
Hope this helps.