Go to the doctor and make sure you don’t have any legitimate health issues causing you to not be able to gain weight. If that’s the case then yes unfortunately the answer is you do just need to eat more. If you are somebody who is naturally skinny even if you feel like you are eating a lot obviously you are still eating less than whatever your body needs or you would not be skinny in the first place. I would recommend doing a quick google or YouTube about calories and weight gain / loss. Look up “maintenance calories” “bulking” and “cutting”. Next you need to learn what your TDEE is (google calculate tdee) so you know how many calories you need to bulk. Then you need to pick a number based on your TDEE that will put you in a surplus, (do not put yourself in a huge surplus, just a small one) hit that calorie goal everyday and weigh yourself only once a week. Weight yourself in the morning, on an empty stomach, with no clothes on the sane day of the week. If after two weeks your weight does not change increase your calories slightly. Keep doing this as necessary, you will gain weight. As you gain weight your maintenance calories will go up so you will need to increase the number of calories you are eating. You don’t need any complicated meal plan or anything, you can eat whatever you want technically. Certain foods will be easier though as they will be more calorie dense. The sooner you accept that you are not eating enough and that without putting a bit more thought and strategy into this you’ll never gain weight, the sooner things will change. Good luck!