Why do I feel so tired after basic strength training?

I'm 147cm, 45kg.

I did a few reps of calf raises, glute bridges, squats and reverse lunges. Took enough time in between to properly breathe and allow myself to relax.

It's morning. I haven't eaten anything. Drank water in between the sets.

But I feel so beyond tired. Puking even. It's not even like I did some heavy exercises.