Hey there - I'm a new mum too, my little girl is 9 days old and was a bit like your little one to begin with... days and nights mixed up. Its a big adjustment for them coming home to this completely new environment I think. She's sleeping much better at night now - we swaddle which I think makes her feel more secure, and she sleeps in the moses basket beside me. I feel the same about the lights, I think if they go to sleep with the light on then wake up with the light off, it is disorientating. What I do now is just leave the curtain open a little so just a tiny bit of light comes in for when she wakes.... I don't know, probably just makes mum feel better!! And I'm looking for a really dim lamp so its just enough to see to feed her by at night without making the room really bright. She has got into a bit of a pattern now, loosely based on the guidance from the Baby Whisperer Solves All Your Problems book, which seems to suit her. Another thing which I would recommend is trying a pacifier. My little one seems to find this a comfort, and is breast fed with no confusion between the pacifier and the breast.... this advice came from my mum and works a treat.
Good luck, its hard when they won't sleep isn't it, we will get there in the end!
Take care,
x