iam a crazy bitxh

my boyfriend and i live together and his brother recently moved in with us. my bf acting strange always with his brother locked in his room. always using his brothers phone. i found out before his brother moved in with us . my bf was texting this girl . the text stopped. i text the girl one day off his phone to ask how they go to meet and stuff . she said she wasnt gonna say anything . next day he asked did you text that girl. his phone was disconnected . so im guessing he is texting the girl using this brothers phone. iam crazy for thinking this. he says he wants more time witj me yet locks himself up with his bro