Panicking

I get like a feeling of deja-vu of things I already seen. Like for example 1 day after seeing something I think of what I saw and I feel "I already saw this before" type feeling, like a deja vu feeling. I have severe dp and depression and all this stuff and I'm 16. I'm so worried of stuff like alzheimers, it feels like I have no memory I'm always forgetting things. When I'm texting I ask the same questions and I don't have any memory of asking them before.