Help just diagnosed today with depression

[ALAN]

49 yr old male fairly succesful have everything i need from financial standpoint but this past weekend have decided to end 15 year relationship with the love of my life our relationship was an affiar to start and actually led to 15 years we are so toxic to each other venomous nothing physical but bad words and yet i am heartbroken about not being with her and also having to go out on my own worried about being lonely and starting new in new house my brain is on overdrive went to doctor today and told me i was in depression now on meds how did this all happen i get that we are not good for each other but love her so much it hursts also kills me to think of her with anyone else although neither of us are looking for that we both have to fix ourselves.

any input much appreciated