am i pregnant/ light period!!! help

i had sex on a monday and got my period that friday, but i have never had such a light period in my life, like it is crazy light. he wasn't wearing a condom, but he pulled out. is there a reason why my period is so light? i have been super nauseous and not eating but i thought it was due to the amount of stress i am under.😢😢😢HELP