how effective is the pull out method?

my boyfriend and i have lots of sex we're 17 so we have to be sneaky about it but everytime we see each other we have sex a couple times sometimes around 10 times and sometimes just a couple most the time we run out of condoms so he has to go raw. and when we use the pull out method he literally cums as soon as he exits my vagina. so i'm a little worried some can get in me. last month i had really weird spotting and brown stuff twice, once at the beginning of the month and again at the end. this month i am supposed to be getting my period today. i've been experiencing PMS symptoms that can also be pregnancy symptoms for the past couple weeks (cramping and sore breasts)