Yes this reply of mine is actually true and to proof it here https://www.mangago.zone/read-manga/heating_up/hs/iur_chapter-77/pg-1/ this is where giovanni lost so much blood that felix donated his blood to him cause he has the same blood type of giovanni
He's having paranoid thoughts. He thinks after he gets cured, Felix's feelings will change and leave him, also because there's no more use on getting warmth from him if he's cured. I also think it's because he developed abandonment issues after he was sent to the orphanage. He said lines like this, because he was really scared Felix will leave him, also this was said in his thoughts, so Felix didn't know what he was thinking:
"I won't let you go. So you should hold on to me too. Even my birth parents abandoned me, so there's no guarantee that you won't abandon me too. You can't leave me [on days like this] because you're soft-hearted. The warmth that you give me is enough for me."
He's really paranoid and scared, poor Gio. Also, he said "On days like this" because it's already rainy season in the manhwa. And Gio gets really really cold on rainy seasons.
I can't remember if Giovanni still has his condition or he was cured of it