A few months ago I woke up with extreme hair loss, I went to the doctor and they said everything is fine. I'm still losing hair, especially with water?

Telogen effluvium. Telogen effluvium is a form of nonscarring alopecia characterized by diffuse hair shedding, often with an acute onset. A chronic form with a more insidious onset and a longer duration also exists.[1, 2] telogen effluvium is a reactive process caused by a metabolic or hormonal stress or by medications. Generally, recovery is spontaneous and occurs within 6 months. We treat with B12 shots every mon.
More info needed. Are you pregnant? Has this happened before? Are there any other signs or symptoms? Is your hair loss is certain spots or diffusely all over? Can other people tell? I would schedule another appt with your doctor and have a list of questions for them and ask for a diagnosis or explanation rather than "everything is fine.".