It sounds like a combination of hormones and lithium side effects. You're on a pretty low dose, but have you had your lithium level checked? And are you drinking enough water to flush out the lithium from your kidneys? Lithium can cause upset stomach.

The bleeding and other symptoms could be anything--pregnancy, stress, pms.

Moods could be part of the bipolar and may mean you need anti-depressant. It's really hard to know. Definitely see your pdoc and primary care doc to assess the symptoms.