Will this help me gain weight?!

sure! the more food the better, provided you eat a healthy diet and exercise. you should gain healthy weight... Make sure though that the peanut butter you are using is natural and organic. Other brands are processed and have a bunch of junk in them! and make sure your eating whole grain bread instead of white
Keep eating a lot of protein. Foods like cottage cheese, yogurts, milk, eggs, turkey, chicken, lean beef, beans, etc
and a lot of carbs! stock up of vegetables and fruits for added vitamins and minerals.. and drink lots of water to keep your skin clear.. and lift weights and exercise so your not gaining too much fat

good luck :]

trying to gain weight myself

well it depends if you want to gain weight, or you are just being sarcastic!!..If you want to gain weight..well eating peanut butter sandwiches 3 times a day won't make you gain weight quick, but maybe a pound 1/2 not, so sure though..and drinking milk is healthy, but yeah it can gain weight if it is not low fat, but milk is healthy for the bones, so it might be helping you with the weight not making it unhealthy for the system.if you are trying to lose it then..you will have to eat better then that, because peanut butter is good for you, but only once a day and milk is very good for the body if it is low fat..just eat vegetables/fruits and drink lots of water then milk, but if you are trying to gain it then, I think you should know what is good for the body and what is not.

hahaha
your gay because your peter pan