i am really confused about this page http://www.mangago.me/read-manga/ashita_no_kimi_wa_k...

I was thinking the same like "what?!"

i know i just don't get it at all!!

I feel like its maybe from sensei's perspective? Like when he loved his sensei but then he got married?

its hard to say. Errors can crop up from translations. I don't think it was sensei's child or that he was ever even in a relationship with that girl otherwise it would have impacted the story more. Also as far as I can tell Sensei is gay. the two relationships mentioned in the story were both with men.