you can have more then 1 slice of cheese.
make the milk whole or raw milk. 2C of that = 300cal
a large salad isn't really gonna help you gain weight.
have some chicken and pasta or something along those lines..
a can of tuna is good, but probably not enough calories. the typical can of tuna is about 90 cal i believe.
cut the skim, no need for that.
but read what the other posters said, add your calories and figure out what your eating. you'll be surprised.