I needd advice

Keo

So about 3 weeks ago i had sex and a few days after i started my period but it was a week early and has been going on for 13 days now should that be normal. My mom told me im pregnant but how if i have my period and i have bad cramps from it to and im scared because i dont know what to do. Is it normal to have a period start a week early and have it go for 2 weeks? Please helpp!! Should i go to the doctor