What are the chances of me to get pregnant after taking i-pill?

Hello,

I had sex and took i-pill. My periods started around 12 days later and lasted for 4 days. I got my periods next month around the same date, which lasted for just one day. So, I took a urine pregnancy test, which was negative. I got my regular periods on the third month as well and it lasted for 3 days. My next periods lasted for just 2 days. I have read on the internet sources that many women get periods during their pregnancy. What are the chances of me being pregnant? I am doubtful because I always used to have regular periods which last for 5 days.

Hi doctor,

The bleeding was heavy in my first month after i-pill. My bleeding is usually very heavy on the first day. I had to change three to four pads on the first day. During my second and third month, the bleeding was too heavy on the first day. My last period was just for two days and as usual, on the first day the bleeding was heavy and I changed three to four pads. I used a pregnancy test kit for testing pregnancy and it shows a single line near to C end. Kindly let me know what should I do. Is it possible that urine pregnancy test will be negative if I do it after a long time conception? Do I need to go to a doctor for ultrasound?