What is wrong with my baby

The other day I noticed he was constipated and he pooped a log out and was struggling it was like a tootsie roll. Then someone told me to put Karo syrup in his formula milk so I did and get shit a lot and it was like paste form and he filled the diaper I thought we were in the clear. But today rolled by and he was the same way all day non stop screaming at the top of his lungs his face turns red like he’s trying to push. He farts a lot but no poop since yesterday. I just don’t know if he’s constipated if he has gas or colic? His symptoms are his face turns bright red when he’s trying to pass a stool, he squirms and screams non stop, he farts but no poop. Lots of thick wet diapers. He brings his legs up to his chest. I want to help him he’s in so much pain the only time he calms down is when you feed him and then if he falls asleep from crying so much but he wakes up crying help he’s 4 weeks and we are on enfamil prosobee