Side effects of anti-depressants?

I've only been on them for about 6 days, but i've been feeling nauseous, and life seems a little surreal. I don't know how best to describe the feeling, it's like my body is there and i'm aware but my mind is somewhere else. My doctor breezed over side-effects, so I just want to know if this is something that happens as long as you're on them, or if it's just the first few days?