I have quite literally ALWAYS had night sweats. They're getting a little worse now. I've always been a bit of an insomniac. Maybe those two things are making this "time of life" a little easier. The fact that I don't panic when I wake up drenched (keep clean nighties in my bedside table drawer, have extra pillows, and just change) ir when I go several days on only several hours of sleep. It's a "been there, done that" thing for me. And of course, it doesn't hurt that I am early-retired. Falling asleep at 5 a.m. when you have to get up at 6 is a ***** -- like I said, been there, done that. Falling asleep at 5 and getting three hours in is much better!
By the way, a freind of mine is 26. She has one child (almost 2 now). She has a family history of very, very early menopause, and was trying to conceive. She was feeling very emotional, and her periods stopped, but her home tests said she was NOT PG. She said she went into crying fits because she was certain that she was going 'through the change' (with good reason -- her grandmother and mother both did in their late 20s, early 30s). Luckily she went to the doctor to see if the rabbit died, and indeed, it had.
And yes, lots of sudden weight loss (or gain for that matter) can screw up your hormones.