Suggest Remedy For Periods Problem

hi, i took next choice two days after I had sex and I got my period two days later than the expected day. I wasn't worried though because it came, but it wasn't like a normal period. It wasn't heavy like it usually was for me but then again it wasn't light. Now I haven't gotten my period and it's been a week and I'm scared I'm pregnant. Is it normal to have irregular periods after taking Next Choice? And how do you know if you're pregnant? Like what are some early signs?