You can, technically. In options of your character (Me) you need to go to (Gender) and choose whatever you like. Also you will need to change prononciation so game could refer to you correctly. Visual atributes can be changed at the mirror in toilets i think.
Also to be able to get knocked up as male you need to pick "anal womb" or something like that. Sadly, it would be easier to make new character if you dont planning to play with mods. But i recomend to. There are convinient mod loader