Why am I so tired

Ok so I’m 26 weeks and 2 days I slept 8 hours last night I woke up made a bowl on cereal and watched tv for about 30 minutes now I’m so tired again I can barely function. I’m not even in my 3rd trimester yet why I am I soooo tired. I can’t go back to sleep because my 14 month old son will be up soon. What can I do to give myself some energy.