Is Pregnancy Possible Despite Taking Emergency Birth Control Pill?

Hi! I'm 22. I had unprotected sex with my boyfriend on May 9th( He pulled out before ejaculation). Then I got period about 2 days on May 15th. Then we had unprotected sex on May 23rd(he pulled out before ejaculation) but early in the next day I took Emergency Birth Control. Today May 29th I have period again.However before my first and second period I took pregnancy test at home. The result was negative. Am I pregnant?