Kate, it's a tough place to be isn't it, where the people you rely upon to help you turn a deaf ear.

Why not begin a journal just for this? Write down your dark thoughts, (date and time too maybe?) and your times of silliness or hyper moods. If you're able, make short notes of what may have added to your mood at the time. After a few weeks of this, you at least will have a good documentation of how you are feeling, and may be able to speak more specifically about it, rather than in general.

Good wishes.