Hi, I think u don't need to worry because ur lifestyle / how active u are will not affect the duration of ur labor (quote from my Gyne). I also didn't exercise at all, never really try to walk, gained 20++kg, baby still on the smaller side and had to eat more by order of Gyne. I asked my Gyne Abt exercise stuff but he said it doesn't matter at all - too many factors affect duration of labor. Fit pple can also have Long labor or end up cesarean so it's really ok. Working out prob helps ur stamina but it's not as though u can control the speed of the labor in the first place. Working out does however lower risk of gestational diabetes and makes it a easier recovery to switch back to somewhat active lifestyle after baby(if u can find the time that is)
U are already 8 months, tired is an understatement. But to improve current situation, I hunk u Shld slowly try to adjust to sleep earlier (just try 30 min earlier, then 60min earlier) so that u won't feel so awake at night n tired in the day.