Many mental illnesses share a common allele. The disorders can be passed down genetically. Mental illness doesn’t have to be expressed the same way from generation to generation—i.e., bipolar parents could have an OCD or anorexic or depressed child. There could be all kinds of combinations. Schizophrenics could give birth to bipolar kids. Depressed parents might have ADD kids. Etc.
What I’m implying is that if you have OCD, is it more likely that your biological parents also have a mental illness. If they do, your mother, at least, could be self-medicating. You do not write about your biological father, or why he and your mother separated. If she has a mental illness, that could help explain the separation, and also why she chose her next husband. I tell you this only to offer you a possible explanation of what is going on. It doesn’t help you figure out what to do, but sometimes understanding helps.
Now, some people say that you first deal with the symptom (alcoholism) and then deal with the underlying issue. My instinct is to think that you should deal with the underlying issue, and then the symptom will go away.
My advice is that you read up about different mental illnesses, and then compare your parent’s behavior to these descriptions. If something matches up, then you have more to go on. In doing this, you should take advantage of your disorder, because it helps you focus on the task, and push yourself on until you complete it in the most thorough way.
If your parents do not think they have a problem, and their behavior continues to hurt you, you could develop options to living in their home. Is your father still alive? Is he a reasonable person? Could you live with him? Are there other family members who would let you live with them? Are there social services that could help you develop options to living with your parents?
A problem like this makes people grow up very fast. It forces you to deal with very serious problems on your own at a younger age than most people in our society have to. One thing you should know is that many children have survived parents like these. Several are on fluther. They moved out as soon as they could, in some cases. It was difficult—very difficult, but they survived, and some say it made them stronger.
This is a challenge for you, and it sucks. However, I have a feeling you are up for this challenge. I wish you the best, and I encourage you to keep asking questions here.