losing weight takes patience. some people need a year or more to see relevant change. doing it on your own is also more difficult if you don't have a friend, family, or trainer to help motivate you and keep you on track.
see a doctor. it may be scary, but you need to make sure everything else is in order before you start any sort of diet and exercise plan. express your weight loss goals and work out a plan.
do some research. you can ask your doctor too. while counting calories is important, eating the right kind of foods is just as if not more so. study up. ask questions. there are thousands of articles on what nutrition to eat and not eat to help lose weight, that taste good and still fill you up. if you have a smart phone, get a calorie counter app. again, find one that breaks down nutrients of what you're eating to fine tune your diet.
even if you aim to lose a pound a week, which is considered healthy, that's 52 pounds for the year. patience and consistency is key for healthy living.
you don't need to join a gym. but you still need some exercise. if it's nice out and safe where you live, start going for walks. 3x a week for 30 minutes around your neighborhood. then increase to everyday. getting your heart rate up a little will help burn calories which leads to fat. then when you're comfortable, look at joining a gym. planet fitness is affordable to many, and is around $150 / year even with their annual fee. they have trainers too and sometimes classes. people of all shapes and sizes go there, so don't feel ashamed going there. you can even look up home exercises you can do on your own. look into ordering some equipment that's realistic for you to use at home and start there. there are tons of videos on youtube as well.
start drinking water. just have a water bottle filled by you for when you're thirsty, grab that instead of soda, beer, or other similar beverages.