Starting a new diet

So my dr told me I need to lose weight. Today I started eating healthy but I’m nervous I’m doing something wrong. I started to walk and exercise in the morning as well. But I don’t wanna eat too little and I end up gaining weight, I don’t wanna eat too much fruit or whatever, I don’t wanna exercise too much is doesn’t work. Plus I’m ALWAYS HUNGRY!!!! Ugh I just want a cookie lol any advice????