im sure this has probably been addressed many times before.
i am 6'2" and only weigh 155.
recently ive been trying to gain weight..only by stuffing my face as much as possible.
im sure this isnt exactly healthy...but im only 19, and not exactly concerned with my health.
what types of food would be best suited for putting on mass?

also, my weight jumps between 152 and 158 constantly.
its where ive been for years.
it changes, seemingly, daily. at times by 5 pounds.
i dont think thats normal...is it?

i think i must have some sort of super metabolism...or quite possibly a tapeworm.

At 19, you probably just have a very fast metabolism; it's not that unusual and it will not last forever. A 5 pound fluctuation in weight on a daily basis is not unusual either. That's just water weight changes. If you have a salty meal, you'll retain more water. If you exercise, you'll sweat it out and weight less. It's normal. Don't worry about it.

Now, do you have any kind of exercise program? Are you trying to gain muscle or just "weight" as in fat? What does your diet look like now? Youth isn't a very good excuse to be utterly unconcerned about your health. I assure you that adopting healthy habits now will make a significant difference in your overall, long-term health AND physical appearance. Not to mention that at least eating healthy foods gives your body more "building material" that it can use rather than junk it just has to dispose of as waste.