I would get your GP to check your hormones, could be low iron etc. I wouldn’t be too concerned about your period being late unless you think you could be pregnant, I’d then start with a test.
My daughter is nearly 11 and i always feel completely exhausted, I do the lions share and also work full time, could just be mum life.
Definitely get a blood test. Do you take any vitamins? I take the betterforyou sprays and take the multivitamin, vit d and b12 and noticed a difference but I still got a blood test and I’m low in folic acid and have slightly increased cholesterol. Also make sure you are eating right (getting enough protein), getting enough sleep etc.