Period Problems for about a month now?

I'm 16 yrs old and yes me and my bf have been having unprotected sex lately and I am a regular smoker and i believe i missed my period this month. I say "i believe to have missed my period" because i have been having period like cramps but no period. I've also been experience nausea and vomiting like twice. The cramps i'm having are painful and they come and go just like menstrual cramps. i have not taken a PT yet because i'm looking for others answers please help..