how has your sex life changed

I am a young FTM. And i am scared that my sex life will take a turn for the worse after giving birth. I'm not uneducated I know it's a muscle and it should go back to size. But in all seriousness I would think that something like that takes awhile. I know that my partner loves me despite the sex but it's something we both really enjoy. I guess I'm just scared of what he will think. Not to mention that this app is a blessing and a curse because you read stories all the time how partners cheat after they have a baby. 
So the question is how has your sex life changed? Does anyone else have or had the same worry as I do? Please leave any tips if you have some.