Personally, I know what you are going through and most of it can be managed with what you eat, when you eat it, and how much you eat. It is hard at first because you have to give up foods you are accusomed to and have to come up with new meal plan ideas.
IBS is triggered or aggrivated by many foods and drinks ie
red meat
cooffee
alchohol
saturated fats
liquid meals
raw veggies and fruits
processed foods (canned, packaged foods)
and many more.....
The foods will eliminate any cramping or bloating and be paitient as it takes up to three weeks for the symptoms to subside.
Also, portion size is soooo important. Our bodies have more trouble digesting and illiminating foods at the same time. So, eat Very Small Portion Size with lots of fibre ie. dried figs, prunes... And avoid eating late at night so just have a snack for dinner and you will feel much better the next day. I am sure you must know Psyllium husk and flax seed help a bit to.
The consitipation is hard without assistance, but you will always be prone to constipation and/or diahrea with IBS but it is a lot about your food. I take a light relaxant/laxative mixture of herbal teas at night which is great and I also get my monthly vitamins through injection from my naturopath (Meyers Coctail).
I wonder if the surgery weakend you immune system some and now you are dealing with not only a gut imbalance but maybe some food allergies. I have a problem with wheat and didn't know the WHEAT FIBER I was eating was causing me to be more constipated. Check into that area. You might want to do an elimination diet. They have information on this on the web but you can also ask your homeopath for help with this.
I'm not sure if this will help but I hope it does. I know this yogurt called Activa and it also has good bacteria in it and it might help with your problem. I think it has probiotics in it but I'm not completely sure. I wish the best for you and I hope this helps.