I'm a guy who's 5'8" and 120 lbs. Nothing seems to make me gain weight.

I've been really thin my whole life, and have tried many times to gain weight without ever being successful. I'm afraid to go on the GOMAD diet because milk causes me to get terrible acne on my face and body.

Everyone thinks it's so easy to just "eat a lot". But when I try to do that, I just feel nauseous and will sometimes actually throw up. I'm a college student without a car, so I can only do limited grocery shopping. I find myself eating out for many meals.

I'm planning on going to the gym as much as possible, but I know nothing about weight lifting. Any and all help from the community would mean a lot.

Edit: I'm 20 years old. Another problem I have is grocery shopping. Every time I go grocery shopping, I find that I never know the right things to buy and I end up with a lot of junk.