How to manage on Linzess

My IBS-C, is the initial diagnosis awaiting more info from tests. Prescribed the Lowest dose of Linzess 72mcg with no change over 1/1/2 months. Now about 1 month in on the 290mcg which I think is working: take with water on awakening and no eating or coffee etc for an hour. About 6 hours later watery diarrhea repeatedly 2-4 times until over by noon. No formed stool at all.
My CT scan two weeks ago showed a large stool load throughout my colon.
If anyone can shed light on this, I would appreciate it. Is this within the realm of what to expect and will things settle down. Any tips welcome.
I have a sliding hiatal hernia (not severe symptoms but occasional nausea and fullness) and silent reflux.
Thanks