Is it normal if i dont want to have sex with my husbant

i am married 5 years and everyday my desire goes lower and lower. And i realise that i dont want to have a sex with my husbant, i just try to avoid it, and if not for its like a violence, every night i go to sleep and imagine some stories with other men, what i should do ? i have a baby with him and he loves me so much and i dont want change him, but i dont feel anythink in sexual life