So last month I was late 12 days and then started my period I thought I had a miscarriage I'm not sure but this month I'm late again and I never have been irregular my periods were always on time and last at least a week

No one here can possibly know if you had a miscarriage.

Is that your question?

No my question is why is my period late again

That's another question here can answer - hormones, infection, stress, pregnancy, something else -

Have you seen a Physician?