Anyone else get sick from Ensure?

I'm pretty much at a loss here. 28, male, duodenum riddled with ulcers and then patches of ulcers through the jejunum, blah blah. For the past week I haven't been able to eat much so based on advice here I turned to Ensure Plus to help keep up my nutrition. Drank it slowly from 11:30 a.m. to 1 p.m., then around 3:15 to 3:30 started getting dizziness, crampy lower abdominal pain and watery diarrhea (unusual for me as my ulcers are near the stomach). Does this happen to anyone else? Could this be just my system getting used to it or am I putting myself at risk of worsening disease by trying it again today? If this doesn't work I seriously have no idea how I'm going to keep myself fed. I'm 150 lbs and usually top out at 800-900 calories in a day before I just can't fit anything else in. Thank you.