How do I speak to my bf about this

TW : abuse

So my boyfriend and I play fight and we don't seriously hurt one another, it's literally just playful and funny for us, but at times he would randomly push my arm or something and I would tell him please stop, I'm not in the mood rn, and he would carry on doing it because he sees me getting annoyed by it, then he does it harder and harder and it triggers me alot because my father used to physically abuse me to the point I couldn't even walk and he would punch my arm till its bruised, so when my boyfriend punches my arm or pushed me or anything, I feel so overwhelmed and I start crying because it makes me think about my dad.

my boyfriend apologizes and he tried to make me feel better but I don't feel better because it makes me feel like he's hurting me like my dad did

I don't know how to tell my bf it reminds me of what my dad did to me, he does know alot about my past with my father but we play fight so we both don't mean any harm to each other and I feel completely safe with my bf, I just don't want him to feel weird that I think of my dad hurting me when he does that, so how do I tell him