A: All small children have a natural impulse to bite, and many 2 year olds develop a phase of biting their mothers (or other people) on a whim or when they are frustrated. Your son has developed a habit of biting which is more intense than usual and is injuring you.
Your first goal is to protect yourself from being bitten. You may have an intuition about the situations or moods which lead up to the biting. Try changing the situation or stepping back before you are bitten. If your son does succeed in biting, say "No!" in a sharp firm tone and with an angry look on your face. Look him in the eye. Step back for a while, but once the moment has passed, try returning to a neutral mood. If your son tends to bite your hands, protect yourself by wearing a pair of clean heavy cotton gardening gloves for a while.
Your next goal is to reduce the amount of frustration that your son is experiencing so that he is less likely to be aggressive and hurt you. The tendency of toddlers to bully their mothers has its roots in the child's recognition that they don't have magic power over reality. Try to see the world from his perspective, and see if you can smooth over some of its stormy moments. Or ask Dad or other family members to handle more child care so you and your son get a break from each other. Eventually, your son will replace his biting habit with more mature ways of communicating and negotiating with you. Just remember that keeping your cool will help in the long run.