I truly, truly, know how you feel. The pain in your heart right now is so deep and there's just no easy way to deal with it. I am glad you are here, though, as you will get support and comfort. You will find yourself needing to vent, rant, rave - and yes, just cry and ask for love. You will get it here.
Your life will have to be pieced back together slowly - as the saying goes, "One day at a time." While that may seem to simple, it truly is the only way to go. Actually, at first it is only one hour at a time, as I am sure you have discovered.
You did all that you could and the "what if's" are necessary for a time. You can't avoid it, so just do it as long as it feels like it is helping. In the end, there will be no answers to them and finding the questions futile, you will give them up. There are no what if's that can be answered adequately.
My son committed suicide, too, and I have been on the journey that you are on now. I am here to offer what advice, comfort, and encouragement that I can. My heart breaks as I re-enter that space and time in my head when I know what you're going through. Just know that I deeply feel your pain.
Stay on here and talk to us when you can.