eating and energy

IR

I'm at 20 weeks, I just finally started eating a little more than just bread because Nausea and Vomiting has been so bad.

why after eating lunch I feel like I've no energies, and I don't remember falling asleep,

but I look at the clock and it's been 4 hr.

this is the 4th time it's happened in one week.

anyone else has this happen, and is it normal?