Leaking sperm is normal after unprotected sex. If you're not trying to get pregnant, you should b using protection at ALL times. When you have unprotected sex and the man ejaculates inside you, it goes where it needs to go and what is left behind is expelled from your body.
Of course its normal. When a guys finishes inside of you, it does drip back out. However, you did have unprotected and he came inside which increases the chances of you being pregnant. If you do end up pregnant, some early signs include a late period, spotting, but the most efficient to find out is taking a test or seeing a doctor.