Idiom
on mindon (someone's) mind
if something is on someone's mind, they are thinking about it a lot or worrying about it.Something's worrying you, isn't it? What's on your mind?I wanted to talk about men but Helen obviously had other things on her mind.I'm sorry if I've been a bit irritable recently but I've got a lot on my mind (= I'm worrying a lot) at the moment.