Inside your mind, what you're thinking about, your ideas, your opinion, maybe your suggestion. Usually about here and now.
Weighing on your mind, pushing you down, making you worried and unhappy, or making you distracted, something that takes your attention away from here and now.
A; You have a crazy look on your face. What's in your mind?
B: I'm going to ask that girl to dance with me.
A: So we can build this in only two years ...
B: The question in my mind is how do we pay for it?
A: Are you listening to me?
B: It's hard to pay attention while I have that girl on my mind.
A: Can I talk to you? I need some advice.
B: Sure, what's on your mind?