Hi, I'd like to help you with your problem.
I am sorry you are going through this. It sounds like you have been feeling miserable about your marriage for a while now.
From what you said, it sounds as if this marriage is not what you thought it might be. You said you were lonely prior to the marriage which might have made the marriage much more attractive than it really ended up being for you. Also, your husband currently uses drugs and that in and of itself can cause major damage to a relationship.
You also mentioned that you are concerned with your adult children and your grandchildren if you should leave this marriage. At this point, you need to consider if your unhappiness and your marriage are affecting the children and grandchildren already. Some people feel that they'd rather have a person happy than stuck in a bad marriage and unhappy.
Although your experience in counseling may not have helped the first time, you might want to consider it again, but with a different counselor if you feel the first one did not help. Sometimes it is just a matter of finding someone you feel you match with, much like you do when you search for a regular doctor. If you do not want to try counseling again, I highly recommend you try talking with your pastor. I'm going out on a limb here and assuming you attend church since you mentioned praying. But faith is a very good thing in situations such as yours. It can provide solace and comfort in a confusing and often depressing situation.
You can try counseling with your husband if you want. If he is unwilling, go yourself. He sounds as if he needs drug abuse counseling and you can suggest it if you want. If he wants to work on the marriage and you are willing to try, a treatment program would have to be mandatory for him.
There are some books that may help you. One is called Too Good to Leave, Too Bad to Stay by Mira Kirshenbaum. Another is Taking Space: How to Use Separation to Explore the Future of Your Relationship by Robert Buchicchio. These are available at Amazon.com or your local library may have them for you.
Ultimately, the decision about your marriage is up to you. It is hard and difficult at best. But you need to take care of yourself and it sounds as if you are the only one worried about the relationship. Getting some outside help from a neutral party can help you sort out your feelings and make a decision. Continue to pray for an answer as well. With help, I believe you will find your way to being happy again.
I hope this helped you,