if u had ur intercourse during the time when u were ovulatin there are full chances of u being pregnant.
because even if u r using a pull out technique there must have been certain amount of ejaculation inside the vagina.
first of all dont worry
consult ur gynaec .
do a urine pregnancy
test ,blood tests and scan pertaining to pregnancy.
secondly it might be just late periods.
repeat ur pregnancy test after 7 days for confirmation if this time upt is nagative.