Can i get pregnant if had sex the day after my period ended?

It's possible but highly unlikely especially if your cycle is quite regular at around 28 days. Ovulation would tend to occur about 14 days after the beginning if your period. Thus conception could occur 5-7 days after a normal period. This is only a guideline, however.

Pregnancy is known to have occured from sex on any and all days of the cycle. You may do a home pregnancy test three weeks after the episode of sex or if you miss a period. . If you do not wish to be pregnant, use contraception all the time, every time. consider implanted contraceptive, or IUD. Practice safe sex :https://www.hopkinsmedicine.org/health/wellness-and-prevention/safer-sex-guidelines

Since your so worried about getting pregnant, than concentrate on practicing safe sex. Many people get pregnant when they don't expect it, because cycles can change and fool you. Anxiety, stress and personal problems can alter your cycle and you feel safe to have sex and than end up pregnant. Never take chances.