¿why you changed it before?,¿you tried to make the characters more realist with the pregnant mod?,like being more slow and heavy making troubles with the jump and the gravity etc...
¿what are you trying to do?,just modify the sprites and don't make complicated things,it's fine too if you want to create and give more realism the skins and mods too but in first place only you need to modify the sprites and don't worry of the others things,the idea is see if the pregnant skin work like a simple sprites skins changes and later you can try and create more complicated things with the help of the others.
about something,¿do you see before these images i uploaded before where the characters using a latex or rubber full bodysuit?,i imagined to change and add some sounds where we can heard these sexy rubbery sounds of their bodysuits but adding new things to the game are more complicated so the most basic thing to do is just edit the sprites to make them wear differents outfits and never touch the parameters and settings of the game if i don't know what im doing.