Don't go, Hai. We are just concerned about you. A lot of us have been in similar situations and have come out of it. Even if it seems impossible it can be done. When I left my ex I had no access to money either - we had a joint account and everything went into that but he had the card so I couldn't access it. He used to leave no food in the house and instead of giving me money to go to the shop he used to leave me hungry at home until he got home from work, then he'd order a takeaway using his own bank account and make me feel guilty for spending "his" money. What's worse is this was when I was pregnant, I needed to eat for the baby! Luckily DS was fine, but I lost loads of weight, by the time I left, I weighed just over 6 stone.
Please ring Women's Aid, even if just for a chat, the number is 0808 2000 247, it won't show up on your phone bill. Don't feel it isn't serious enough or that they will laugh at you or think badly of you - they will care and they will listen, and they'll only give you advice if you ask for it.
I know it's scary to think about leaving, but this is because he has made you totally dependent on him. Come on, how many evenings do you sit there with your stomach churning worrying about what you have done wrong this time? Do you not want something better for you and your son? There are so many wonderful blokes out there who really and truly will love you for YOU, and let you be that person, not try to keep you so close they crush you. You deserve so much better. You deserve that night out once every 3 months! You are young, don't let these years pass you by. I have only been on my own for 6 months, but my life is so much better now. The house is calm and my little boy is so much happier. He still loves his Daddy and still gets to see him, even though he told me he wouldn't see DS if I left, and in fact they spend much more quality time together now than they did when we were together, because even at weekends etc I was always "in charge" of DS.
You can do it - don't worry about the money etc. It will sort. There are people and organisations out there who will help you if you'll only reach out and ask for that help. You have posted here which is great, just keep posting, or ring women's aid, or both. It's all going to be okay