Blue was with the doctor for too long. Too long that it gave Winter the time to think about everything.
'How could I have been so careless? How dare I leave Blue all alone when I fully know that he's pregnant and has pheromone disorder? What the fuck is wrong with me??'
The whole idea of him and Blue not living together in the same house had never appealed to him front the start. The only reason why he never brought it up again after Blue told him for the first was because he didn't want to come off as too strong.
He was too prideful and had hoped Blue would realize that living alone was sad and lonely, which would make him give up and return to Winter's house.
Winter had forgotten to account for the fact that Blue was the most stubborn person in the entire world. He'd rather suffer and die in silence, than admit he was wrong in doing something.
Winter all too familiar with Blue's stubbornness, yet he'd let him be.