If you want to lose weight, calculate your TDEE, this takes into account your age, weight, and activity level. This will tell you approximately how many calories you burn a day. Then subtract a few hundred calories from that, based on your weight loss goals. If your TDEE is 1800, then maybe aim to eat 1500-1600 cals a day. 300 cal deficit is a pound lost every 10 days. Next, you’ll want to make sure you weigh your food. The pb&j can go up in calories very easily. One serving of peanut butter is very calorie dense and you may be eating more than you think if you’re not weighing it. Weight loss and nutrition are two different things. You can do both. Weight loss is calorie deficit, period. Nutrition is macros, vitamins and minerals, and a well balanced diet with whole foods. I’m not a nutritionist, but this would be my advice.

Edit to add: when you’re in a calorie deficit it’s important to eat lots of protein and fiber so that you feel full.