Husband blames and criticizes me for everything

One enters into marriage with dreams of hoping to start a new journey with their partner that is filled with love and happiness. With the basic respect and responsibility not met and enduring a feeling of being blamed and criticised by your partner is certainly not why someone enters into a marriage. Moreover, even your child is bearing the brunt of this. I can imagine your pain and agony.

Before moving on any further, ask yourself if you are willing at all to give a chance to this marriage or not. Also try to figure out if your husband is willing to do the same. For a happy and successful marriage, both partners need to be equally invested to work towards it. If either of you are not willing then the choice is for you to make whether to stay in the relationship or to leave.

If you are willing, then what you could do is to try and figure out what is making your partner criticise and blame you. Are you both on the same page about both your expectations of this marriage?
Try to understand the roots and cause of his nature. Are most of his other family members or close friends also of the same nature? Or are external factors like work pressure or tension being expressed out to you in this manner?

Once the reasons are figured out, communicate with your partner your concerns in a way that does not sound accusatory but rather an opportunity to work towards a solution.
Saying "Stop blaming me for everything!" is less productive than saying something like "I feel hurt when you blame me for our issues. I wish you would appreciate me a bit more for what I bring into this relationship. I want us to take responsibility in the marriage and mutually figure out what we can do to resolve our issues together. After all, our son is also getting affected by this". Using more responsible words rather than accusatory words is more likely to invite the other to think towards a solution than to aggravate the issue by getting instigated.

Start small. Take up one small step towards making one small change in one of the barriers you found to your issue. Gradually increase in addressing to other steps towards as many issues as possible. Remember, consistency is the key. Even if it is only one step that you both have decided to take on in a long time, it is okay.

If you choose to leave, as difficult as the process might be, it would help for you to avail counselling services that will help you through the difficult journey such as adjustments to living alone, getting support, handling children in divorce, finances, considerations for legalities, etc.
It is only natural for you to be worried about how your son might be affected in the process, but remember, staying in an unhappy marriage also has its influence over the child.