How come when I have sex I struggle to make noises?

Yes I am enjoying it, it's not a case of them being bad in bed but I do also have a low libido. I'm too self conscious to moan in bed and I'll hold in the noises. Even when I'm on my own and masturbating I still find it more pleasurable to hold my breath rather than to make a moaning/screaming orgasm noise. It's really frustrating because I know how much men hate mute women but I feel way too uncomfortable to make and noise and if I do, it's me forcing it out and it's not often. This is ruining my sex life and making me more uncomfortable in my own skin.