why does my bf gets turned off if I say I am thinking about us ?

Maybe fear of commitment? Probably best to ask him, rather than guess. And ask yourself what you mean when you say it.

He’s attaching a negative emotion to it. You are likely thinking about the two of you in a loving way but he may have had bad experiences where he was conditioned to think that it means the opposite

Might equate it to judgement and/or pressure regarding your relationship.

Thinking....hmhmhm he has separation anxiety from past and thinking about it may mean, leaving etc.lol, which i doudbt you really mean.

Because it's obvious you are trying to manipulate him. Do you want to be manipulated 24/7 by a scheming significant other?

Commitment issues. No strings attached

"There you go having to bring feelings into it again."

Not enough context here 🤷🏻‍♂

Oof nothing worse than a grown man afraid of commitment

What does said "thinking" about the two of you usually lead to ?

he doesn't like women to think