It shouldn't affect me

My dad doesn't call me much and when he does it's mostly negative, I guess I kinda feel down atm because he's not who I need right now. He's in pain or has a problem and I have compassion but when I tell him I'm in pain he just laughs at me. It's so difficult to talk to him also because the day before I would have a conversation with him and he acts like he doesn't have any recollection of anything that was said and says I'd have to think about that one, at this point I don't know whether he's doing it on purpose or he's got something wrong with him. I feel like I don't even know who he is.