Why do you need to drop out of college because of your low weight? Are you not physically able to handle getting around campus, or is it embarrassment? You shouldn't quit college out of embarrassment!
Have you been to a nutritionist? Depending on the size of your college, there may even be one on campus that you can see for free. You are worried about your weight, but if it seems that food just runs through you without stopping, then you may also have a vitamin/mineral deficiency. A doctor or nutritionist can help you with that problem. Sometimes you can gain or lose weight due to your vitamins and minerals being out of whack.
Also, have you studied the sumo wrestler's diet? They gain weight on fish, rice and vegetables--all very low fat stuff. How they gain the weight depends a lot on when they eat and how much. A friend said she had watched a documentary on it a whlie back and there was something about them getting up and doing all of this weight training first thing, then not eating until late afternoon--where they had a huge meal--then eating a huge meal again at supper, with no more activity for the day. Oddly enough, their fat is under the skin (subcutaneous), not around the organs (visceral), which is supposed to be much, much more healthy. In fact, there's some evidence that subcutaneous fat has no bearing on your health at all, unlike visceral fat.