Welcome Yeahtomyself: I'm sorry you are having a tough time.
I've abused alcohol and lied and hid things from her. I feel a tremendous amount of shame about what I have done and have been trying to better my life. I quit drinking and lying - abeit it has only been a short time - and am trying to clean up the many messes I have made in my life.
I'm glad that you quit drinking and that you are working on yourself. Hang in there. It isn't easy and sometimes the road isn't in a straight line. Do you have support to help you? (AA, friend, etc.)
I have read about tactics for dealing with people with BPD but have difficulty implementing them. I'm so depressed and feel helpless to change things.
What tactics have you tried? It takes some practice. I don't think most people have instant success.
Some of the lessons below can be helpful:BLAME AVOID CIRCULAR ARGUMENTS FOG - DEALING WITH FEAR, OBLIGATION AND GUILTSETTING BOUNDARIES COMMUNICATIONS OVERIVEWYou might find the first two links most helpful for you right now. Give it a try. I will take some practice. You have some of your own challenges to face, but you can do this. Let us know how it goes.