I am only a day late. But my periods have always been irregular

4 or 5 minutes? That's a long time. You could be pregnant.

But what if he didn't ejaculate in me.

There are plenty of sperm in the early fluids, so even using a condom there is a chance, but sounds like you used no protection, so there is a much higher odds than using one.

But less odds than if he completed.

But could you be, yes of course that is the result of sex, a baby

Possible... sure, but not likely. It is not uncommon for a period to be off a couple of days here and there, and since your periods are naturally irregular you won't really be able to go by that.

Give it another week and if still no period, try a test. If negative... give it a bit more time, and test again or wait and see what happens with your period next month.