You used to hate blueberries, but now that you're older, you've come to love them. And the blueberries look delicious. Usually it's almost impossible to pick a carton of blueberries where they all look good, but that's not the case here. Every carton is perfect.
The sign says something about them being perfect for gay couples trying to conceive, but you don't read any more than that and the price, which is very affordable. If you had read the sign, you probably would have moved on. But you didn't, so you buy a carton.
When you get home, you decide to dig into the blurberries right away. They go bad so fast, after all. You wash a handful and sit down at the table. The moment you swallow your first bite, your body changes. Your internal organs shift and change, allowing for a new uterus, though you still have your "male" equipment.
You're still a man. But you had still been horribly changed because you didn't properly read the sign. Anyone who eats the blueberries becomes a pregnant man. He still has his penis and balls, but will have have a uterus until he gives birth, which will be done anally, as he doesn't have a vagina. When he gives birth, he gives birth to both the baby and his uterus. However many blueberries he eats determines how many months he is. Before you stopped due to the transformation, you had eaten...