Hi Nichat. I'm so, so sorry that this has happened.
Please understand that your dear partner took the action that he took for reasons entirely to do with him. I'm sure that he truly loved you, and your son, your mutual love shines through your posts here, but something tragically awful took him over, this was reality for him at this time, and eclipsed that love. Depression is a cruel illness for everyone. 
I lost my beloved DH earlier this year, and was devastated; please be very, very kind to yourself. Simple things can work very well, like a hot cup of sweet tea and a slice of hot buttered toast. It may only give you 10 mins of calm but that's invaluable when your mind and heart are racing.
Accept all and every bit of support that's offered. Eat well, drink plenty of fluids, and take some exercise - I walked, still walk, a lot which I find very calming.
Take small steps. Only one step at a time. Things will improve, given time.
My heart goes out to you, and your dear son. I hope you manage some sleep, or at least, a more peaceful, calmer night.
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