Kinda confused

So my boyfriend and I had sex last Sunday and I was close to coming but then he stoped because he came but I quickly got on top of him but he still had cum and my ovulation was 6 days ago so basically a week and I was on the safe side, 3% chance but i don’t know I don’t want to risk it but then again I don’t want to spend money if I don’t need it . Should I get a plan b or do you guys think I should be okay.