I've heard I won't be able to control my bladder after pregnancy. Is this true?

That's what you heard. That's also why you should do your Kegels to strengthen your pelvic floor muscles as much as possible. It is true that childbirth weakens the pelvic floor muscles, but honestly speaking, I wasn't very diligent in doing my Kegels and gave birth naturally but I am able to control my bladder.