I normally get my period on the 20th of each month regularly. This month I had unprotected sex on the 11th and the condom broke and a little sperm was on the outer walls of my vagina. I got my periods 4 days later, that is the 15th. Is this normal? Or am I pregnant? Will a blood test/pregnancy test stick show if I'm pregnant just a few days after sex?

No a pregnancy test will not show up anything for several weeks, normally you need to wait till next month and see if you miss that period or not.
It could be just the period coming early. Periods are not always exactly the same.