Can I get pregnant if I had sex a day after my period ended?

Probably not but.... It depends on how long your total menstrual cycle length is and how many days of bleeding you have. For a 28 day cycle you most likely ovulate on CD13-14, If you have 5 days of menses then you probably didn't conceive. However, if you have a 25 day cycle you most likely ovulate on CD 10-11. If you have 8 days of menses then it's technically possible to conceive. Consider contraception.