I haven't experienced anything like your loss, but I know way too much about dark places. Even when things get really bad please try and reach out to someone whether they are family, friends, people here, your doctor, or one of the many helplines. Check locally to see what is available in an emergency. Alcohol and drugs(prescribed/recreational) can feel like they help, but they are the equivalent of putting a band-aid on a compound fracture.
Talking and sharing is the best way and don't be afraid to cry. Do be careful of forums that are dedicated to this sort of loss as there are alot of weirdos out there preying on genuine people. Also; go out in the middle of nowhere and scream, shout and swear like a madman. You need to release your emotions in whatever way you can to keep the dark thoughts at bay.
Big hugs to you and stay strong.