I had sex 4 days ago. I should be getting my period today or tomorrow but I have an irregular cycle. Could I be pregnant and how can I stop it quickly?

Plan B can only be used 3 days after unprotected sex, you can still try it (It is most effective after 24 hours but... ) You should go talk to your doctor they'll know what you can do.

Problem is that I don't live in the country and I don't have one. I just don't know what to do

You could try calling a doctor if there is none around you, they can give you some suggestions. How old are you? Could you talk to your mom/grandma/aunt?

Assuming because you wrote this in child/teen, that you are a fairly young teen perhaps ?

You need to discuss this with a adult and get in to see a local doctor where you are at.

I would go see a doctor and have them test you that is one way you can be certain if you are pregnant or not

How old are you? The reason I ask is this is in the teen forum and it's better to know your age in order to give you the correct advice.