Hi Bandy, as both hospital stays were some time after you started Humira, have you discussed pausing the therapy till it gets better? Perhaps your immune system can't deal with stomach flu viruses good enough while you're on that med.
As your doctors ruled out c.diff, they should have done norovirus at the same time.
If you do not respond to bactrum within 3 days you might switch to standard pouchitis antibiotics Cipro & Flagyl if you can tolerate them.
I guess you are dealing with chronic pouchitis or ileitis since you have to take biologicals? How did your severe diarhhoea start - very rapid within a day or slowly building up over some days? For me a norovirus or even more c.diff hit me within a short time, while bacterial disorders were more like a gradual development.
I can't give much advice about liquid stool. One idea is to strengthen your digestive system by adding bitter herbal extracts to your food, but in hospital they often don't administer natural meds.