How to take back control?

I have a 12 year old son who seems very domineering and controlling and I feel it was because I treated him as an equal since he was little. Letting him make decisions and not wanting to discipline him harshly. I was treated really poorly as a child and I did not want that for him. So I think I went overboard the other way, not enough discipline. How can I fix this and get back on track? Please has anyone else had this problem? He is not domineering or controlling in a bad way and he is in no way disrespectful, he just demands full attention and he tries to push his way into adult conversations.