You are not alone (I'm a single mom with 3 kids) and it is very difficult. Like
@Sighs, I'm a "yeah, me too BUT I'm not there now"....but I'm not naive enough to believe it can't happen again. However, I've worked very hard to put things in place to make it as unlikely as possible. That includes not drinking (well, very rarely, one drink - when I'm with friends and stable), working on keeping my emotions regulated, learning to recognize if I've been triggered or am sliding into depression, working on distress tolerance and grounding strategies, taking care of myself, self-nurturing, etc.
That said, it sounds like you're in a place right now where small steps...just making it through the day or the hour or the minute...are what you need to do. Are you in counseling? Do you have a doctor who can recommend medication (I haven't had any luck with medication, but many others have)? Have you considered a DBT skills group (this has literally saved my life)?
When I was in that place, I did get a book on adult survivors of parental suicide. It was hard to read, but it kept me focused on how much it would damage my children. And I had a counselor who was very blunt about the effect it would have on the kids (he basically said he would use anything he had - even guilt and shame - to keep me alive).
And the guilt...yes. Would my kids have been better off with a parent who was mentally stable? Sure. Do I feel guilty about that? Yes but not so much any more - but it certainly was something that ate me alive when I was depressed and suicidal. Today I focus on today - what can I do today to keep myself safe and happy and by doing so, become the best parent I can be. Oh, and letting go of the perfect parent thing...that's a hard one too, but it will also feed into the self-loathing if you don't.
The nasty thing about suicidal depression is that it convinces you that it is forever. It doesn't have to be.