She WAS part of his life before you. I am 50 years old and if he is writing an album about his ex that means he processed his past and it’s part of letting go and moving on. If he is with YOU now then that is intentional, he wants to be with you. The only thing that can ruin the relationship is your jealousy. Let it go and go be good to your man (iff he treats you well)… let it go or there will soon be an album about you too and you don’t want that!!!!