i had sex on april 20, took postinor 2 on april 22, withdrawal bleedin on April 26 or 27 and lasted for no more than a week. another bleeding came exactly 28 days after, on May 25 and it looks like a period. lasted for 6 days. urine test is negative until now. i feel a bit nausea every morning but might be because i havent eaten. could i still be pregnant?