Its totally normal for babies to grunt, strain, cry, turn red, and roll around while pooping. Newborns are using those muscles for the first time, and it takes a while to hone in on how to use them properly.
I would find a chiropractor for him.... and if you are nursing.. only nurse on one breast per feeding. A forceful letdown will cause gas and irritable baby, or reflux like symptoms, so only nursing on one breast per feeding will get him the hindmilk he needs to grow and thrive, and also it will fill his tummy. If you are formula feeding, its proablby the formula. Its very hard to digest and newborn systems are not meant to break down anything but human milk.
I would be VERY hesitant to give a newborn any type of medication, especially reflux meds... its pretty harsh on their systems, and usually doctors treat for reflux when its not reflux at all, just a baby getting his bearings to new food, new environment, using his body outside the womb, etc. I do'nt think reflux is as abundant as everyone thinks... babies are cranky, babies cry, babies strain to poop, they even spit up, especially babies on formula as their body has to really work to digest it.