I don’t remember how I gained weight exactly, but I remember one thing my doctor recommended I try. Not sure if you have a Trader Joe’s in your area, but they have this thing called cookie butter, and that’s something my doctor recommended I snack on with so graham crackers.
Makes for a great snack, so if you can find it I’d highly recommend it. It’s not the best advice, but it’s all I got. Good luck in your weight journey bro