any advice?

i screwed up my birth control and had unprotected sex and he did not pull out. well my period is supposed to start next week tues and this past week ive had EXREMELY vivid and odd dreams, my back has hurt, cigarettes have been giving me a headache and i have congestion issues going on and today i started having faint light pink bleeding and it doesnt even fill a panty liner and is mostly there when i wipe. how possible is it for me to be pregnant?