Its different now

Ok. Current situation. Oral feels different since I had my baby. He's 4m now. I've tried to express it to my partner.I cum, don't get me wrong. But then its starts to hurt. Its hard to explain. He's the best head I've ever had but something has changed. It hurts him and he lashes out. I tried to explain but he's not hearing me. What do I do? How do I make the man I adore, understand, that its my body and not him?