I mostly had issues with diarrhea. My understanding is its because you no longer have bile stored on the gb to deal with digesting large amounts of fat in one go, instead you just have a steady trickle entering the system. This means you have 2 types of potential irritants entering the bowel: either undigested fat or the bile. I don't know if that explains the constipation or not, but it does the diarrhea. I guess that could be a question for your surgeon.

I have found it best to avoid large amounts of fat in one go, but try to focus on including healthy oils in my diet throughout the day. I also upped my fibre intake (which seemed counterintuitive when you're going to the toilet too often and because I already eat a lot of veggies etc) and especially added in psyllium but then I switched more recently to inulin (which dissolves more completely and is also a prebiotic). Apples and pears are particularly good. I also use probiotics more often now which seems to help, and I used bovine colostrum for a while too. Whenever I get sick now (eg virus or whatever) it seems to upset the digestion, so I start up the fibre & probiotics etc and that sorts it out in a couple of days. I guess none of that could hurt if constipation is your problem, just make sure you are drinking loads of water as well.

PS activated charcoal capsules are good for gas pain.