You're likely more sedentary, or not going to bed early enough to deal with when you wake up.
This is a common thing for people to start doing once they start working. Here is how you get back to sleeping normal amounts:
Stop drinking all caffeine by 17 hours before you need to awake the next day to get to work in time (so if you have to wake up at 7 to get to work, stop drinking it by 2pm; you may think it doesn't keep you up, which may be true, however it does make you sleep less deeply). Try dimming your entire house/apartment 11 hours before you need to leave for work, turning off all screens, read, listen to soft music, etc for that hour before bed. No watching TV or doing anything other than sex and sleep in bed.
Then go to bed 10 hours before you need to leave for work, have a real bedtime.
Do this for about 2 weeks, and you'll find you are so mentally alert. You'll feel like your old self in no time.