We never put a mattress protector on the Moses basket mattress but have had a waterproof one on the cot mattress. Always had a double layer of fitted sheets on the Moses basket though, to deal with those inevitable middle of the night sick-ups more easily.
I don't know whether my bump is low or high, but definitely having a lot of heartburn the past while and my lower ribs are really sore, feels like they're being stretched out! Baby was head down at my last appointment, but I keep feeling a big knobbly bit rolling around at the top of my bump. Had similar with DS - always thought it was his head, but turned out he just had a very bony bum!