Baby constipation

My son just turned 2 months on the 19th. He struggled with passing bowel movements often. He is both breast fed and formula fed. His pediatrician said if he starts getting uncomfortable because he needs to pass a bowel movement, to give him 1 to 2 teaspoons of Karo syrup to help him. It’s been 3 days since he’s had a bowel movement and he’s getting really uncomfortable. I’m not sure if we’re supposed to give him the light or dark corn syrup. Has anyone used Karo to help their little one with constipation, and if so, was it the dark or light one?