I'm 23 I have 3kids and have had my tubes tied. My periods have come late in April and May 3 to 6 day. And now this month it didn't come at all. I have some light pain in my back and sides.

No, this is not an ER situation. It is a regular GYN concern, although your period might just have skipped a month, or you might be pregnant (very low odds).
'My periods have come late in April and May 3 to 6 day' - what does that mean?