I had unprotected sex two days ago and my period has always been extremely irregular so how early can I take a pregnancy test and get reliable results

You will want to wait till about one week past the end of when your period was suppose to happen. So you wait, till period is due, it does not happen ( or is very light) and wait one more week and then test. If negative, wait two more weeks and try again.

As far as I know you need to be pregnant for about to weeks but there is some home pregnancy test that you can do before an expected period.

But I have no clue when I should have a period because It is never at the same time and sometimes I only have one every few months.

Test about 2-3 weeks after the time you had unprotected sex.

But I have no clue when I should have a period because It is never at the same time and sometimes I only have one every few months.

Two days after unprotected sex is way too early. You're not even "pregnant" at that point.

Wait 3 weeks. If you haven't had a period, which you may not because you're irregular, try testing then. Make sure to use first morning urine, and follow the directions of the pregnancy test to the letter.

If it's negative, then wait a few more weeks and test again if you haven't gotten your period. Another option, which is more accurate, is to go to your doctor for a blood test.

Good luck. I send baby dust your way, as you're obviously trying to conceive. :)