guys help!!!

So I just had my bby 3 months ago. & I had sex with my bf for the first time after birth. I'm breastfeeding. BUT he finished in me. I haven't started my birth control yet. & im 2 or 3 weeks with my period being done. CAN I GET PREGNANT??? I'm so paranoid now!! I don't want another child so quick. Idk why he finished in me I thought he was ganna pull out ugh ! Advice please!