to go back you'd either have to go back a save or take a transformation pill that removes your tits (Titsbegone)
the red pill makes you keep you transformations and there is no way to reverse it back after that other than other transformation pills, the blue pill removes any transformations that you haven't taken the red pill for(aka any ongoing transformations that you can see through the effects tab below your character animation box) and will remove the transformation completely
be sure to unbox the content for others to force give you the red pill unless you like that happening