Do you know why my period is irregular? I haven't had a period in so long?

I haven't a clue why your period is irregular. I haven't had the chance to run the blood tests.

How old are you?
When was your last period?
Are you sexually active?

Yes, of course, without seeing you, without any medical tests, blood work, cat scan, we know all your medical info.
LOL,
There are 100s of causes, from just happens, to life threatening reasons. Where do you want to start ?

If it continues, time to see your local doctor