Feeling fatigued

This semester has got to be one of the most tiring for me. I have a 10-hour teaching stretch on Tuesdays, including 4 hours in the night from 6 to 10pm. My Tuesdays start at 8am and don't end till 10pm. I don't get to see the girls in the morning and I don't get to put them to bed at night. I hate that.

Wednesdays see me rushing to class early at 830am till 3pm with a 2 hour lunch break in between. Fridays are somewhat similar.

My only respite are Mondays (free day) and Thursdays (1.5 hour lecture). But somehow there is always lots of work to clear on these 2 days.

It doesn't help that I find myself lecturing a lot in these classes. I talk so much in class that after that, I find myself clamming up to preserve my overstretched vocal cords.
This has never happened to me before in my 7 years of teaching. This is the first time I feel so tired. Is age catching up on me or has my passion for teaching waned a little?