Whatever's on my mind, or has been on my mind...
For example, I'd start by saying, "I feel guilty about..." or, "I feel like you've had enough of me," or, "I'm having a hard time dealing with this friend...," or, "There's something on my mind but it's so hard for me to talk about it, could you help me along..," or "I feel like one huge failure..."
She's usually very helpful in helping me express the rest of 'the story'.