Loving poem sent to me but was wrote and sent to ex should i be annoyed?

my partner writes poems and they are really good and i really enjoy reading them especially some of the loving romantic ones they made me feel so special. he sends me loads on facebook so when hes at work i can read them and they do really put a smile on my face. well today i was on his facebook and was being nosey and reading his messages. i know i shouldn't but curiosity got the better of me. well anyway i was reading some of the messages he sent to a girl he was seeing ages ago before he met me and i found the same poem he sent to me which he lead me to believe it was wrote for me. im annoyed but more hurt. do i have a right to be considering i looked at his messages?