When to seek help - right now. It's never too early. I agree with sophiesmom. Once your depression get too bad, finding therapist or seeing a doctor seems too much work. If you seek help earlier, you may require fewer sessions.

Medication - In my case, my therapist and doctor suggested to try it. My doctor told me to clear up medical issue first (some physical condition can mimic depression or anxiety). When we cleared up I'm physically healthy, he told me to see therapist first. If therapy alone is enough, we don't need to take medication.

I would see primary care first, and see what they say. If they only recommend medication, you can also ask referral for therapy.