Waking up too early

M28, construction worker 37-45 hours , running 50km+ a weak, working out 2-3 times a weak, eating healthy, melatonin, glycin and magnesium before bed.

I don’t have a problem falling a sleep at night, but if I wake up in the middle of the night I can’t fall back to sleep.

If I sleep through the night, I wake up 1-1,5 hour before my alarm, feeling kinda fresh, even if I only have slept for 6,5 hours. I really want my 8 hours, and going earlier to bed, just me makes me wake up earlier.

I don’t read before bed, I’m laying with my phone, and the room temperature and not cold.

But is this really the reason for me to wake up so early?