I lost my family!

I am utterly lost in despair.  My ex-husband and I were married for 31 years, and raised three awesome sons.  My boys and I were so close their entire lives.  I was the hands on parent, and loved it!  My sons and I did so many things together - snow skiing, water skiing, hiking, Trap Shooting, Traveled.  I was at every baseball, football, wrestling practice and game, cheering them on.  I was at all their school functions, awards ceremonies, school plays.  I was a Youth Group Leader at our church, where the boys and I attended, and they were active in all the church activities.
We had so much fun!  We laughed, we could talk about anything, we teased each other.  And I was their go-between for difficulties they had with their dad.  We shared everything....except when their dad became an alcoholic, mixed with prescription paid medication.  I didn't tell them how bad he had gotten; and I didn't tell them that he had become mentally, emotionally and physically abusive to me the last 3 years of our marriage.
I should have told them.  In hind sight I believe they would have come to my defense immediately.  But I was embarrassed and ashamed, and didn't want them to know what their dad had become.  I lied to them about the black eyes, bruises, etc.
When I finally HAD to leave - suddenly, to be safe - they were all shocked, hurt, angry....
But they ended up most angry at me!  Their dad told them lie after lie about me - that I had put us in financial ruin, when in fact I had been the sole bread winner for 3 years.  He told them I was on Coke, and Meth, and any other drug he could think of.  I went to the hospital and had a blood drug test taken to prove to them this wasn't true.  It didn't matter.
He told them I was a Lesbian and I had left him for a woman.  Anything that went on during the divorce, he made it sound like it was all my fault and I was just out to ruin him. 
They bought in to his lies, because I refused to sink to his level and drag them into the divorce.  Within three months none of them were speaking to me.
It has been eight years now, and none of my sons will see me, speak to me, or even acknowledge me as their mother.  I have one granddaughter that I haven't seen since she was two, and I have three grandsons I have never met.  One of my grandsons died of cancer at 13 months...I never knew him.
I put up a brave front, but feel like I just sludge through each day, without meaning.  I go for months and think I am finally resigning myself to the loss - then suddenly I am falling apart, crying unconsoleably. 
I hate living this way.  I miss my sons.  My granddaughter Jamie looks just like me, but I never see her.  I fear I never will.  I am an only child, and my widowed mother is not in good health.  I worry continually that I will die alone - just as my ex said I would.  I worry about what will happen to me when I am old and can't take care of myself.  I worry about my children and grandchildren - my ex is an evil pervert, and I am sick thinking about how much time and influence he has over  the grandkids.
I don't even know what they are mad at me about, other than I left their dad.  When they were still speaking to me, they would say things like "Geez mom, I don't know what your problem is.  He hasn't hit you in several months."  or "He told us he only hit you once.  Can't you just forgive him?".
I didn't just lose my sons, I lost my life.  They were my life.  I pray continually, attend church, talk to God, see a counselor; but my days roll one into the other.  Ditto. Ditto. Ditto.  Groundhog's Day.  My heart and soul are as dry and parched as desert sand.