Lady problems!

I'm eighteen years old and I have had sex quite a few times but I can never cum and it's barely enjoyable. I never cum when I masturbate either. I always get bored with it and just give up. I also have problems getting wet but I continue to have sex even when I'm not wet by libricaring with saliva. My boyfriend spent half an hour down there and it just wasn't doing it for me.. I see porn where the girl is arching her back and moaning and I've never experienced that either. Lately I've been noticing my sex drive is low as well. Does anyone know what's wrong with me? i am on mirena for birth control if that helps anyone but I've also had sex when I wasn't on birth control. Thanks in advance.