No, basically when he was overseas and his health was deteriorating he spent a lot of time asleep, and when he did he dreams that he is with Iwa and his daughter and that him and Iwa can form a bond (which they cant bc omega and beta). So he loves his dreams. But when he wokre up overseas he "wakes up in a nightmare" because he's away from Iwa and her.
Oh no definitely all the time they spent together was real I didn't mean to make it sound like it wasn't. But the dreams are from before he came back to them. They're flashbacks to when he was still overseas. Tho i did say he dreamt about both iwa and their daughter now that I reread it I realize it was just about iwa. Which makes sense since he didnt really know his daughter lol

Oh, wait! Did something happen when Oikawa went overseas or something?