This is a little long but I just wanted to share what has worked for us in the last few weeks in case anyone is going through something similar!
DS was a very "easy" and content baby for the first week of life and around 4 days old developed a raw rash around his anus (sign of allergy/sensitivity) that wouldn't go away with any kind of cream, oil, zinc oxide, breastmilk, etc. After that he started being very fussy and cried in pain for hours a day. He also started projectile vomiting. I eliminated dairy from my diet and started looking into other things while I waited for that to leave our bodies (about 3 weeks).
He had a couple of chiropractic adjustments that would help for a day or two and then he'd go back to crying in pain. After a perfect birth and extremely fast recovery, I was really struggling that things had become so difficult. I felt really down and guilty for not enjoying having a newborn and sad that he was so unhappy and uncomfortable after every effort to make his entrance into the world as easy as possible.
Exactly 3 weeks after eliminating dairy, his rash cleared up literally overnight, with no change in our diapering routine, and hasn't come back since. He was still crying a few hours a day though.
When he was a month old I took him to a craniosacral therapy session. She said the sphincter and membranes at the top of his stomach had become inflamed and enlarged from the dairy sensitivity and were sticking up toward his ribcage now that the inflammation was gone. She gave me a couple of simple exercises to do at home and said in about a week the membranes would gradually go back to the right place and he should be better.
Sure enough, a week later and he woke up a totally different baby! He had chiropractic adjustment that day as well to fix a tight spot in his neck and he has been a completely happy baby since - no more crying in pain, he doesn't have the apprehensive look on his face anymore, and he's starting to smile now. He'll be 7 weeks tomorrow and it looks like the colic is gone for good!