You won't spend the rest of your life feeling that way. A broken relationship can indeed lead to depression, if you let it. Start going for walks. Exercise and sunshine are natural healing.
Think about what might have been. You may have been married, with children and a home. That is as bad as it gets. Happened to me but I got over it, took me two years and I drank a lot. I mean, a lot. But eventually she meant nothing, in fact I hate her badly, still because she stole my kids.
I see the kids who are now adults and don't ever see her. I live in another city.
I would suggest seeing your doc and getting a referral to a therapist.
DOn't ever forget thought that crying is our body's way of trying to heal us. It's ancient and works but is painful to go through. I used to be afraid to cry as it felt so lonely but I always felt improved afterwards. Even briefly.