My mind

Can my mind trick my body into thinking I’m pregnant? I don’t want a baby and I’m so scared. I had sex 2 days before my period came about 2-3 weeks ago . I had constipation before I had sex and all that but I still have constipation, I have stomach aches, I have the urge to poop but I can’t, I have chest pains ugh idk what’s wrong.