I recently found out that i am pregnant with my second child. Ever since then, my 2year old have been behaving very weirdly. He have been screaming and hitting me despite me trying to talk to him in a calm manner. What is happening?

Be patient and pay extra attention to him. Somehow kids have the sixth sense, sort of they know something big is goin to happen and will change their life. You can try read to him books about being big brother, or watch videos about babies. Maybe visits some relatives who has babies and let him experience of holding the baby. Hope this will make him excited and lead him towards behaviour that suits his role as the 'new' big brother.