I suppose not all people think the same way.

I'm not multi-lingual; English is my only language.

But I don't think primarily “in English”. English is a tool for communicating with others, and not for internal thought processes, which are usually more complex and more directly representative of that of which I am thinking than any combinations of English words I could put together to try to describe them.

For example, if I am thinking of putting on my shoes, I do not think of a string of words such as “I will pick up my shoes, put them on my feet, and tie the laces.” I think of the actions themselves, not of words to describe the actions.

Language isn't really relevant to my thoughts until I think of communicating them to others. I suppose that if I were multi-lingual, then what language I would think in, when I thought in a language, would be determined by what of my available languages I believed would be most readily understood by the person to whom I was thinking of communicating. If I'm not thinking of communicating, then language really isn't relevant.