Unprotected sex (pullout method) after withdrawal bleeding?

Nina
Hi! I'm a college student with a fairly active sex life and I'm just wondering what the chances are to get pregnant from unprotected sex, with my partner pulling out when he ejaculated are? I just finished withdrawal bleeding that lasted three days after taking an ECP give or take two weeks ago. 
I'm planning to take an ECP since we had sex just a few hours ago, but they have terrible side effects on me so I'm hoping that I can skip them if my chances of getting pregnant are slim. 
I'd really appreciate some insight!