Will i still get pregnant if i had unprotected sex 4 days before my period? and if my period is late for around 3 days, does that mean i'm pregnant?

Usually not: For a woman with a 28 day cycle, she is fertile 14 days before the next period is due (plus or minus 4 days). So unless you have a really short cycle with a period every 20 days you aren't fertile 4 days prior to your period. If you are 3 days late for your period you might be pregnant, but sometimes periods vary when they start by a few days, or are delayed due to things like high stress.