Trying2moveon, one of the hardest things about life is that nothing ever goes back to what it was - what you had is gone and for all of us in some way shape or form. While we don't like change life is ever evolving and changing and the key is to move with it by letting the past belong where it is, be the the past.
There is however nothing stopping you from being more than an existence other than yourself. I know you won't like to hear that but, from what I have learned, it is the cruel harsh reality and truth. You have made a start by coming to this forum. Now, if you want a different life and for your heart to stop breaking then the only way to do that is to take one step forward at a time. What small change can you make in your day that will help you feel a little better? I remember devouring books and reading and reading just to get 'unstuck' as that, to me, is where you sound like you are - stuck.
If you exist for your children's sake then take that and use that to help motivate you from 'trying' to 'doing' as the simple reality is that to be the best mother you have to look after yourself first. I am sure you believe your children deserve more than you just 'being there' as you sound unhappy and they would see that. Find one thing to make yourself smile each day and you will also reward your children. I believe you can bring happiness back into your life and I believe that if you put one foot in front of the other you will slowly but surely be able to find you way to a better life.