I agree that staying together for the sake of your son is not a good idea. No child should have that pressure put on them, and they will know it eventually. That being said, it sounds to me like there is hope for you anyway. You have to look at your relationship with him as separate from your role as mom. Being a parent is not the same as being married. They are two separate things. When you want to work on your relationship problems, don't think of him as your child's father, think of him as your significant other that you love.
Men and women communicate differently. And their brains are wired differently. We will never fully understand each other. But it helps to know how they are "built" so you know where they are coming from and why they are acting a certain way. Check out some books from your library on communication skills, specifically in a marriage setting. Read anything you can about making relationships work. Then make him read the ones that you think are relevant to your situation. He needs to understand how your brain works too. Then you might be able to start getting along better.
Not to push religion on you, but a church would be a great source of help if you are so inclined. I know some churches will offer free counseling sessions. My sister and her husband (whose relationship sounds exactly like yours, by the way) recently joined a church and one of the reasons was for this counseling that they offer to every member. I don't think you should just go find a church to take advantage of free therapy, but you might find that you benefit from the church in other ways also. Who doesn't need a support network?
I got married very young as well, and it is difficult even if you don't have a child. So here is my last piece of advice- every time you have a fight or get angry or even just every night before you go to bed, stop and ask yourself this. Is it worth it? Do I love him? Would being without him be worse than this right now? If the answer is yes, then you can work through everything else. If you ever answer no, then you know where you stand. I hope everything works out for you, and I wish you the best!