if you have a 28-30 day cycle then yes you could be pregnant, your ferile days range from about 25-29 oct for a 28 day cycle and 27-31 oct for a 30 day cycle, so you had sex on the 24, sperm can live for four days so that falls in that period and again on the 29 and that falls within the time for a 30 day cycle, all you can do now is to wait and see if you miss your period then test using first morning urine
What makes you think you can't? Sex is meant for reproduction, and unprotected sex only ups those odds. Take a pregnancy test if you think you are.