Don't worry about
losing weight. I didn't lose any because I ate a tiny amount every 2 hours. Just stock up on clear liquids like broth and gelatin, milk supplement products like Boost High Protein if that's available, and strained soups. Cream of Rice cereal is also a good one for a little later when you start to add texture. You won't want to shop for a couple of weeks.
If you change your diet habits right now it will be easier later. I ate all the bad stuff before and now don't. A couple of months on good food is enough to teach you that it really does taste better. Forget sodas, learn to like tea or decaf coffee with sugar and milk.
If milk doesn't agree with you try to see right now if you have a lactose problem or if you don't tolerate the milk proteins. If you can take lactose-free milk, that answers the question. You have to get nutrition somewhere. Adding Whey, a milk protein, is helpful.