In what language are your thoughts formulated?

Over the years I’ve had a lot of people ask me this question and I have never been able to give them an answer, the main reason being that, whenever the question comes up, whatever thoughts were in my mind at the time seem to suddenly vanish and when I try to figure out what language they were in, I come up blank. I’ve tried to figure it out on my own several times but, again, I always lose all my previous thoughts and am finding it almost impossible to answer this question. It’s quite frustrating…

So, if you’re multilingual, do you know what language you normally use in your thoughts? If so, how did you figure it out? And did you have as much trouble as I’m having figuring it out or do you just know?

Thank you :)