Very broke and getting slimmer x)

Dry beans and canned tuna are great protein sources that are cheap and frozen vegetables are usually cheaper and sometimes more nutritious than fresh.

I agree, you need to add some type of vegetables. Whatever is most affordable for you. Frozen and canned are comparable nutrient-wise as fresh, as long as you don't overcook them, and generally cheaper, especially if you can find them on sale or use coupons.

I enjoy getting the maximum nutrition out of a single chicken. I put a chicken in with new potatoes to stew for the day in my slow cooker on Sunday, reaping a whole bunch of meat, potatoes, and home-made chicken broth. The potatoes were fried up as hash browns the next day, and the chicken served with an Alfredo sauce. I packaged up the rest of the meat for three more meals, and I just used half the broth and some of the chicken to make white chili tonight.

I make a chicken casserole that's pretty cheap and I eat it for about a week.
1 chicken breast baked and shredded
1 can cream of chicken soup
1 cup of dry brown rice cooked
diced celery, spinach, carrots and onions and garlic... or whatever veg you like sautéed together
1/2 cup parmesan cheese
1 cup sour cream
mix it all up, put it in a baking dish, top with some bread crumbs and bake at 425 until golden brown.

This makes quite a bit of food and freezes pretty well

I'm not sure what is available for location and cost (for equipment if you have none yet, license, etc.) where you live, but fishing and hunting are some ways to add protein to your diet. Fishing is generally easier, safer, cheaper. It sounds like you have a lot of carbs presently (oatmeal, rice, pasta) in your diet, so that may be a way to get some protein on the cheap.

As well as the ideas above, I make yogurt from milk.

Its important to get enough protein. When you lose large amounts of weight (your profile says 50lbs), the body can use muscle as well as fat as an energy source.

I try to include enough protein in my diet to minimize the amount of muscle loss. Its takes a lot of time and effort to build muscles. Even if it costs a bit more, I think its better to keep what you already have !

I agree with all said above. I have had times like that with less money...and I was living in dormitories with only one kitchen for a whole building(which you have to reserve in advance). Partially for lack of time, partially for other reasons, I didn't take that challenge well at the time and also ate a sort of a diet of a number of things over and over, just as you mention...except mine was may be worse. Since I rarely got to cook, I would be waiting for my money to arrive, eat one good cooked meal for the week(bought out- it was some cheaper deal) and then the rest of the week I was on bisquits/croissants, coffee, white cheese, some bread, lots of noodles and soup "cups", cabbage and things like that...(basically the cheapest things where I was at the time- though not the cheapest if I found time to cook, but that's a whole other thing...).
My point is, while I was my skinniest at the time(no surprise there:P) it did also get me to malnutrition and took me few months to get myself to normal. I know it's hard having money trouble, but try to be creative and have more balanced meals still.

definitely not protein powder, power bars....what a rip off!
On the other hand, homemade soup goes a long way and is pretty reasonably priced. Tuna, frozen veggies, frozen fries fill me up and are cheap (some would argue they arent healthy but they are kind of a staple of my diet)