How should I go about loosing weight with stomach problems like diverticulitous gastritious might have hernia too?

Eat less/move more. The key to weight loss is always eating less calories and moving more. I suggest that you exercise for 30 minutes daily, walking is fine. Also make sure that the food you eat is nutritious, no junk food or empty clories like sodas or sweet snacks. Eat lots of fresh fruits and vegetables as tolerated. Take a probiotic daily on an empty stomach.
Life style change. Start an active life style
Eat less at a time
don't skip meals
eat healthy breakfast
use salads
avoid soda
avoid sweets
avoid carbs
drink plenty of water
exercise daily.
Calories in n out. See the excellent answers on "weight loss". You basically need to burn more calories than you take in. Increase your exercise, choose healthier, less-caloric foods and drinks. The nice thing is that if u build more muscle you will even burn more calories while you sleep! and don't focus too much on weight. Focus more on pants-size, etc. Muscle weighs more than fat but that's ok--its good wt.