My baby is 4 months old and I'm starting to introduce bottle to him with my pumped breastmilk but he is refusing and cries endlessly. How can I make him take the bottle?

Its normal with latching babies. I encounter it before I head back to work too. My girl will reject the bottle but gradually and slowly reduced the number of latching and fixed it at a time. For instance myself, since im working, I will let my mom (caregiver) bottle feed her from 7am-7pm and then take over the latching from 7pm to the next day 7am. Slowly, my girl get used to the schedule. Don't worry. It takes time. Jiayou!