Let's deal with the main thing first: you will not sleep well, and that is not a sign anything has gone wrong.
Tents on every route but one
Machame, Lemosho, Rongai, Umbwe and the Northern Circuit are all camping routes. Two-person tents, pitched before you arrive, taken down after you leave. Marangu is the exception: it has permanent huts with bunks and mattresses, shared dining rooms and, at the lower ones, running water. That's Marangu's real selling point, and the reason people pick it in the wet season.
How cold it gets
Camp temperatures drop below freezing from about the third night, and the last camp before the summit can be minus ten or colder. You want a sleeping bag rated properly for that, not optimistically. Hire one in Moshi or Arusha if you don't own one, it's cheap and it's a sensible thing to hire rather than buy for one trip.
Being warm enough to sleep
A few things that work. Put a bottle of hot water in the bottom of the bag before you get in. Change into dry sleeping clothes, because the ones you walked in are damper than they feel. Wear a hat. Use a sleeping bag liner, which adds real warmth for very little weight. Ask for a second sleeping mat if you're a cold sleeper, since most of the cold comes up from the ground. And eat something before bed.
Why your breathing goes strange
Lots of people at altitude experience periodic breathing as they fall asleep: it speeds up, then stops for a few seconds, then starts again, often waking you with a jolt. It's common, it's usually harmless, and it's alarming if nobody warned you. Mention it to your guide anyway, along with anything else.
Toilets
The public long-drops at the camps are basic and get worse as the week goes on. A private toilet tent, carried by its own porter, is an extra on most climbs and is one of the few luxuries that nearly everyone says was worth it. Bring your own paper and hand sanitiser either way.
Washing
A bowl of warm water morning and evening, and that's it for a week. Wet wipes, a small quick-dry towel and dry shampoo are the standard answer. Everyone is in the same state, which helps.
Noise, light and the small hours
Camps are busy, crews are up early, and tents are not soundproof. Ear plugs and an eye mask weigh nothing. You'll also be getting up in the night to pee because you've drunk four litres: keep your head torch and your shoes where you can find them without a search.
The night before the summit
Barely a night at all. You reach the last camp in the afternoon, eat early, and lie down around seven to be woken at eleven. Almost nobody sleeps, and the people who spend that evening worrying about not sleeping have the worst of it. Three hours of lying still in a warm bag is enough to set off on, and the adrenaline covers the rest.