could i be pregnant??

so i didn’t have my period at all in january because i was so stressed and then on january 22nd i had unprotected sex and he used the pull out method. on january 28th, i starts spotting but it was brown and lasted for about 3 days and then it was gone. i’ve NEVER spotted in my entire life. a couple mornings in the days following, i woke up slightly nauseous and later in the night my back was starting to hurt a bit and i’ve been having mild mood swings and i’ve been VERY tired lately. my next period was supposed to be from january 31st- february 2nd and it hasn’t come yet. could i be pregnant??