Why does my boyfriend say that he can't see me sad but has slapped me twice out of anger and says mean things to me?

We've been together for 2 years. And till date he has never apologized for his hurtful words and actions even after confrontations. Everything is normal for him. But he says he can't see me sad and everything will be fine after marriage. But I'm not really happy and worried, insecure about what will happen after marriage. I have even Expressed these things to him but he only says that everything will be fine and I'm just overthinking things. Am I really overthinking? Am I wrong here? What should I do guys? Please go through it and suggest me. Thank you so much for reading.

Why does my boyfriend say that he can't see me sad but has slapped me twice out of anger and says mean things to me?
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