Yup, dd is also 2 1/2, and it's a lot better with the night wakings now that she's night-weaned and sleeping in her own bed, but I'm still crazy sleep-deprived.
For us it was that up until 16 months or so, we were still co-sleeping and nursing through the night. She would wake up every 90 min or so and keep me awake another 30-45 min, then go back to sleep, only to wake up again in 90 and repeat cycle. I was pregnant at time so I was beyond exhausted and we couldn't figure out any other choice but to night wean.
Now that she's in her own room and almost 30 months, she wakes up about once a night and now I've attributed it mostly to being too hot or too cold or wrapped in blankets. I think her first reaction is to wake and whimper or call out "Mommy!" - sometimes she's already asleep again by the time I'm peeking in her door. And about once every 4 nights, she sleeps all the way through.
A few other things that work for us - feeding her something at least 90 min before bedtime... trying to really pay attention to what temp seems to be her "perfect temp" in her room and trying to add/subtract clothing and blankets to match it... of course keeping her physically active during day helps... and suprisingly I notice that she sleeps better through the night if she has her nap during the day. At daycare she takes naps daily, but on weekends she often won't go down for one, but I'm noticing when she does it's a lot better that night. So not I'm back to really trying to make sure she naps when I've got her all day.
And you are NOT alone on the not losing weight thing - I have struggled so much to lose weight and people keep asking me if I'm pregnant (I"m not now, and they asked me for 2 years when I wasn't before as well). So I feel you... and I know that sleep is key to that weight loss, but haven't quite mastered the sleep thing yet.