Keep in mind that we are HUMAN as well as bipolar. I differentiate between a bipolar depression and a normal depression, we're allowed to have normal depressions jsyk.

Bipolar depressions are biochemical, normal depressions are situational - for example if you lose your job, or if someone close to you dies. But yes, normal depressions can trigger a bipolar depression, but not always.
Depends on a lot of things, with the medication I'm on now - I can be sad because of normal issues (omg it feels so good!) without it spiraling into a depression. But before that; every little stress-factor would explode into a depression. There was no middle grounds, no normal feelings.

I agree with Lbien6. Btw, I'm not in therapy anymore, I don't need it. If you don't need it, then don't go. We usually don't have problems that can be fixed by just talking anyway, not any more than Jane and John Doe does.