Breastfeeding and energy levels

I’m currently 15 months into my breastfeeding journey and for the past month I’ve just been exhausted. I make it about 5 hours into my day before I start yawning and am just tired.

I wake up around 2 times a night still (for 15 months). I eat relatively well, prioritizing whole foods and protein. I take a beef organ capsule once every other day.

What can I do to feel better? Or is this just normal since I’m nursing so often?